DiffPDF Changes

Our ecommerce provider, MyCommerce (owned by Digital River Inc.) stopped paying us (and it appears, many others, see The Register) in August 2024.

We no longer trust any ecommerce provider. We do not have in-house expertise either in security or in tax regulations, so we are not able to handle payments ourselves. In view of this Qtrac Ltd. has now ceased trading, and will be wound up in due course.

We recommend that any customers with unacquired license keys acquire them as soon as possible. We hope to keep the website going for a while, and we hope to keep providing support as long as possible. All keys will continue to work as before. In particular, “full” keys will continue to work so long as the hardware/BIOS doesn't change, and annual keys will continue until their normal expiry date, regardless of hardware changes. Our software does not “phone home” and does not depend on our website. (In fact, some customers use our software entirely offline.)

We are very sorry for the inconvenience to our customers, and grateful for all those who have purchased our PDF comparison software over the past decade.

Qtrac Ltd. is selling its console command line PDF comparison software, comparepdfcmd. Although comparepdfcmd has proved a successful product in its own right, it is only a thin wrapper around our Rust-based PDF comparison engine. This engine could also be used in a GUI PDF comparison application, or to provide the back-end of a web-based PDF comparison app. Interested parties should contact mark@qtrac.eu for a prospectus.

This software is for sale or resale in the US and most countries outside Europe. (Why?)

6.1.1

• License clarification.

6.1.0

• Switched to annual license keys only. These are not tied to the hardware and may be transferred (moved) freely from one computer to another. These licenses can be purchased singly. (Existing “full” license keys continue to work normally.) Click Help→About to see which kind of license is in use and when it expires.
• License changes.

6.0.8

• License changes.

6.0.7

• We strongly recommend setting the number of cores DiffPDF uses to the number of cores in your CPU, since doing so may provide a considerable speedup if the automatic core detection has underestimated. See the manual's “Improving Comparison Speed” section.
• Library updates.
• License changes.

6.0.6

• The Register Copy button has been reenabled. The problem is due to a Windows clipboard reliability issue. If copying the Computer ID fails, open C:\Users\<username>\cid.txt in Notepad and copy it from there.
• Minor internal improvements and library updates.

6.0.5

• The Register Copy button has been disabled since it doesn't currently work. To copy the Computer ID to register a license key, either type it manually, or better still copy it from the file C:\Users\<username>\AppData\Local\Temp\cid.txt.
• Dragging and dropping files no longer works reliably so has been dropped.

6.0.4

• This version is significantly faster on Windows 10 than on Windows 7.
• Minor internal improvements, library updates, and a tiny error-message-related bug fix.

6.0.3

• Minor internal improvements and library updates.

6.0.2

• Various minor internal improvements and library updates. These should make some comparisons slightly faster.

6.0.1

• Various minor internal improvements and library updates. These should make word-mode comparisons slightly faster in some cases.

6.0.0

• Added support for high quality PDF report output. Version 5 produced its PDF reports by “photographing” pages from the original PDFs. Version 6 copies the actual pages from the original PDFs. This is faster and means that if the original pages are scalable, then the report will scale too, i.e., you can zoom in as much as you like on the report PDF and it will always be clear and sharp.
• Various minor internal improvements and library updates.
• DiffPDF 6 is a 64-bit application that requires 64-bit Windows. DiffPDF 5 continues to be supported and remains on sale for the benefit of those who require a 32-bit application.

5.9.5

• Added support for doing appearance mode comparisons with the “new” renderer. In some rare cases the “old” renderer doesn't detect some texture or gradient fill differences—but the new renderer does.

5.9.4

• Updated libraries, including the PDF library.

5.9.3

• The first time DiffPDF is run it will automatically attempt to acquire a free trial license key over the internet and be ready for use immediately. (This means that the very first startup may take slightly longer than normal.)
• Updated some libraries.

5.9.2

• Usability improvement: if you ask for a PDF report, when the report is ready you are offered the option to view it in your PDF reader.
• Updated libraries to make DiffPDF slightly faster and use less memory.
• Log files (which were normally empty) are no longer created.
• Updated and clarified the license.

5.9.1

• Updated some libraries (bug fixes and a tiny speed improvement).
• Updated the license.

5.9.0

• Updated to use a new PDF library that supports the new PDF 2 standard, in addition to the existing PDF 1.x standards that previous versions support. In many use cases the new library uses less memory and is faster.

5.8.2

• A new .csv report format can be chosen by checking the Report option's New CSV Format checkbox. This is more robust than the old format and is compatible with new product developments.
• Acquiring a free trial key should be a tiny bit easier since DiffPDF now attempts to pre-fill-in the Computer ID.

5.8.1

• Optimizations have been applied to the Standard text comparison algorithm which produce noticable speedups in many cases. (The most important optimizations are only available in 64-bit editions. These editions can run more than 10% faster—depending on the PDFs being compared—at the expense of using more memory.)

5.7.0

• Replaced the options tabs with an easier-to-use combobox plus options panels combination. This also takes up much less vertical space.

5.6.8

• Added a new Ignore Hyphens checkbox in the Text Modes tab. This defaults to unchecked. If you check it hyphens will be ignored. This means that, for example, one–two is treated as onetwo. This works even if two is on the next line.
• PDFs (and therefore reports) can now be zoomed up to 800%. (The previous limit was 400%.) Zooming takes more memory and CPU time, e.g., 200% takes 4x the memory and CPU, and 400% takes 16x the memory and CPU, so zooming beyond 400% is best used only on a high performance computer with plenty of RAM and using a 64-bit version of DiffPDF.

5.6.7

• Updated—and slightly faster—PDF library.

5.6.6

• Improved PDF report output to use Portrait/Landscape more appropriately when outputting the changes for only one of the two PDFs.
• Tiny minor internal improvements.

5.6.5

• For report types that have titles, the title now shows each PDF's filename with its full absolute path (previously the absolute or relative path was shown).
• Added a new Path in Title checkbox to the Reports tab. This is checked by default in which case DiffPDF has the same behavior as previous versions, but which if unchecked will mean that report titles contain filenames without paths.
• Added a new Compare Zoomed checkbox to the Appearance Mode tab. (This is only needed in very rare cases as explained in the manual.)
• Improved error logging.
• Various internal improvements.
• Updated some of the libraries that DiffPDF uses.

5.6.4

• Fixed a bug which caused missing pages to always be the size of the first page rather than of the corresponding page. This only affects PDFs which have different numbers of different-sized pages.
• Updated the PDF library. This improves rendering and accuracy in some quite rare cases.

5.6.3

• Added an Always Compare Afresh checkbox—default unchecked—to the Application tab. If checked, DiffPDF will not cache its results, and will perform every comparison from scratch. This is useful if one or both PDFs is being changed between comparisons.
• Allow the zoom to go up to 400%—this is fine (although maybe slow) for viewing, but is not recommended for PDF reports as it would make them extremely slow to produce. (For reporting, the zoom is best set to 100% or 150%.)
• Updated the PDF library. This improves rendering and accuracy in some very rare corner cases. Also, the library is slightly faster.

5.6.2

• The Swap button now not only swaps the two PDFs, but also their Pages.
• The Application tab's Save Memory checkbox now defaults to being unchecked. We recommend unchecking the Save Memory checkbox unless you are comparing large (1,000+ page) PDFs and need to save memory.
• Updated the About box and License to ensure LGPL compliance.

5.6.1

• Added a new Save Memory checkbox to the Application tab that is checked by default. If unchecked (and after DiffPDF has been restarted), some rare PDFs that could not be rendered before (and therefore could not be compared), will now be able to be rendered and compared—at the cost of using a lot more memory.

5.6.0

• Password-protected PDFs should now be comparable again (providing you enter the correct password).

5.5.2

• Fixed bug that prevented the change bar from being switched off, and now correctly remember whether the bar is on or off between sessions.

5.5.1

• Added a new Report PDF Changes checkbox that if checked will cause DiffPDF to watch the PDFs and report if they are changed in the status area.
• Minor bug fixes and improvements.

5.5.0

• Added a new “Multi-Column” comparison algorithm that can produce much better results for multi-column PDFs than the Standard algorithm. The comparison algorithm is set in the Text Modes tab.
• A new Column Tolerance option is available in addition to the existing Line Tolerance option—both of these are set in the Text Modes tab, and either or both can be used to tweak the Multi-Column algorithm's behavior.
• Added a new Normalize Ligatures checkbox in the Text Modes tab. The default is unchecked (the current behavior). If checked, ligatures are treated as if spelled out, e.g., fi = fi, fl = fl, etc.
• DiffPDF is now available as a 32-bit or a 64-bit application. The 32-bit version will work on 32-bit and 64-bit Windows, whereas the 64-bit version will work only on 64-bit Windows. The advantage of the 64-bit version is that it does not have the 2GB memory limit that 32-bit applications have. This makes it possible to compare huge PDFs using Appearance mode—providing the machine has enough free memory.
• Comparisons now use less memory—considerably less when using Appearance mode.
• Numerous minor improvements.

5.3.1

• The license has changed to allow for a license key to be reissued at most once, within one year of purchase. In effect this allows a key to be transferred if a computer breaks or is replaced. For the precise terms, see the diffpdf-license.pdf.

5.3.0

• The Computer ID used for license keys is now based on the CPU and Motherboard only, and is no longer dependent on the BIOS. This means that license keys issued on and from 2015-06-26 for version 5.3.0 and later will not be affected by BIOS changes. Old license keys will continue to work (providing the BIOS, CPU, and Motherboard are unchanged).

5.2.1

• Comparisons are now faster in many cases.
• It is now possible to set up to 20 rectangles to exclude (the limit in previous versions was 5).
• Clicking the PDF views will only set corners, margins, or rectangles if the Show Options checkbox is checked—this is to avoid setting them accidentally.
• Updated some of the libraries used by DiffPDF. This should ensure that some very rare PDFs that couldn't previously be rendered are now rendered correctly

5.2.0

• Eliminated some rare false positives.
• Fixed a bug in page range handling that caused problems in some rare cases.
• Increased the pairs limit (how many pairs of pages can be compared as if one very long page) from 1,000 to 5,000. Setting pairs to 1 (the default) and using page ranges is still to be preferred.
• Subtle user interface bug fixes to ensure that comparisons are redone when appearance comparison settings are changed.
• Small and subtle user interface improvements, including new icons.
• Updated some of the libraries used by DiffPDF.

5.1.2

• Added a Copy Exclusions button to the Application tab: click this to copy the excluded corners, margins, and rectangles to the clipboard in .dpc format ready to be pasted into a diffpdfc .dpc configuration file.
• Updated some of the libraries used by DiffPDF.

5.1.1

• Bug fix: rectangle color and style are now correctly applied.

5.1.0

• Added support for arbitrary rectangle exclusion (in addition to the existing support for margin and corner exclusion). This means that any arbitrary rectangles anywhere on the page can be excluded from comparisons.
• Corners and margins exculsions now use whole numbers of points to be consistent with rectangle exclusions.
• Appearance accuracy now uses whole number percentages.
• By default the Control Panel always appears on the left of the window, with the two PDF View Panels in the middle and right. It is now possible to choose any one of four window layouts in the Application tab:
  
• It is now possible to set the “Missing Page” text to any text you like in the Appearance tab's Missing Page Text line edit.

5.0.0

• Added the Accuracy option in the Appearance settings tab. By default appearance mode comparisons compare every corresponding square exactly, pixel for pixel, i.e., comparison accuracy is 100%. In some situations it is useful to consider pages that are almost identical to be the same—this can now be done by setting the accuracy to less than 100% (e.g., to 99% or less).
• Added support for remote deployment (i.e., bypassing the Register window and avoiding the need to use the .msi installer on individual computers), for customers who buy at least ten licenses.
• Unlike version 4.x, password-protected PDFs cannot be compared. We hope to reinstate this functionality in a later 5.x release.
• Implemented a new license key scheme, and updated the license terms to match.
• It should now be possible to compare huge PDFs (those with thousands or even tens of thousands of pages).
• Improved the comparison speed. For PDFs in the tens of pages the improvement could be 5% or more; for PDFs in the hundreds of pages the improvement could be 30% or more, and for thousand page plus PDFs the improvement could be 40% or more.
• Reduced memory consumption by up to 50% for large PDFs.

4.1.6

• In some rare cases a valid license key could wrongly be identified as invalid: this has now been fixed.

4.1.5

• Reintroduced the .log report type since some customers are using it.

4.1.4

• Bug fix. If the number of cores cannot be detected the program defaults to 1; previously it silently failed. This can be overridden by checking the Show Options checkbox, clicking the Application tab, and setting the Cores spinbox to the actual number of cores the computer has.
• Dropped the .log report type.

4.1.3

• The maximum square size is now 144 pt to allow for coarser-grained appearance comparisons.
• The license key is more robust in the face of changing network configurations.

4.1.2

• Added .log report type that produces basic summary information.
• Fixed a bug where PDF report pages got smaller and smaller.
• Added a paragraph to the license clarifying use within virtual machines.
• Changed all website and documentation links from diffpdf.appspot.com to www.qtrac.eu.

4.1.1

• Bug fix. In rare cases PDF reports could be missing a page; this has been fixed.
• Now gives a percentage indication of approximately how different the PDFs are overall.
• Tiny cosmetic change to the button layout.

4.1.0

• Improved speed—up to 10% faster for book-length documents.
• Added a “Swap” button to make it easy to swap the left and right PDFs.
• The page list view now gives a visual and percentage indication of approximately how different pages are.
• Added indicators to the toolbox tabs to make it more obvious that they are clickable and whether they are “open”.
• Improved the button arrangement.
• Bug fixes. PDF filenames and page ranges can no longer be changed during a comparison.

4.0.5

• Subtle algorithm improvement which eliminates some rare false positives.
• PDF report headers now end with the program name and version rather than just the program name.

4.0.4

• Bug fix. In rare cases margin exclusion didn't always work correctly in text modes—this has now been fixed.

4.0.3

• Bug fix. Whitespace is now fully normalized. This means that all whitespace characters (space, non-breaking space, etc.), are treated as a space (i.e., as a word separator)—this reduces false positives in some cases.

4.0.2

• Improved PDF library: this produces more accurate results, but can be slightly slower for book-length documents.
• More attractive splitters.

4.0.1

• Startup is now much faster.
• The line tolerance algorithm is now specified by name (Standard or Special) rather than by number.
• Tiered price discounts are available when buying at least 10 licenses.
• The About window now shows the computer ID. This is useful for identifying the computer for those who have bought multiple license keys.

4.0.0

• Added a Show Inserted/Deleted Pages text mode option. This can result in more understandable results in some cases when using a Pairs setting greater than one.
• Changed how license keys work so that they are now tied to the computer DiffPDF runs on rather than to the licensee's name. The Register window has been updated to reflect this change.
• Changed the license terms to match how the new license keys work.

3.5.1

• The automatic setting of Pairs to the page count of the longest PDF now works correctly. (Previously it only worked the second time Compare was clicked.)

3.5.0

• It is now possible to compare password-protected PDFs—providing you enter the correct password when prompted.
• Completely rewritten the code for handling page ranges. This fixes a bug. It has also resulted in comparisons between page ranges being faster—much faster in the case of comparing relatively few pages out of PDFs that have many pages.
• By default the Pairs is set to 1 at startup. It is now possible exercise more control over this setting's behavior.
• Applied various small bug fixes including using the correct (logical) page number in the title of PDF reports.

3.4.4

• Added an additional command line option to make it more convenient to run DiffPDF from within another program.
• Added a tiny Visual Basic example function to show how one might call DiffPDF from a Visual Basic program.
• Some internal changes so that DiffPDF and diffpdfc might be able to coexist in the same directory—although this is not recommended or supported.

3.4.3

• Updated one of the libraries that DiffPDF depends on.
• Finally found and fixed the problem where in rare cases the Register window would say that a valid license key is invalid.

3.4.2

• Applied another fix to stop the Register window saying that a valid license key is invalid.

3.4.1

• Changed the default insertion highlighting color to cyan (from blue); and changed the default highlighting x extend to 4.0 points (from 2.5). Since the highlighting settings are remembered between sessions, we recommend upgraders manually set the new defaults to try them out.
• Changed the selection rectangle's color from cyan to green.
• Applied another fix to stop the Register window saying that a valid license key is invalid.

3.4.0

• It is now possible to copy selected text to the clipboard.
• Some tiny efficiency improvements.

3.3.3

• Tweaked the main window so that the splitters take up less horizontal space and slightly reduced the space within the window's borders—all to make more room for showing the PDFs.
• Introduced a new (and hopefully final) fix to stop the Register window saying that a valid license key is invalid.

3.3.2

• Implemented a new more robust and general fix for landscape-oriented and other rotated pages. Now the page views and all reports work correctly for rotated pages in all modes (Appearance, Characters, and Words).

3.3.1

• Fixed the handling of landscape-oriented pages, that is, pages rotated by 90°. The page views and visual reports now correctly show the whole page with differences correctly shown. Text reports' differences now have the correct coordinates. Note that while the Appearance and Words comparison modes work correctly for landscape pages, currently, Characters mode does not. (Fixed in 3.3.2.)
• Fixed the change bar that is shown in the page views and visual text mode reports when the Preview First Page checkbox is checked so that it is always visible even when the page views and reports are zoomed to less than 100%.

3.3.0

• Added support for passing PDF filenames on the command line to help those who want to automatically invoke DiffPDF as part of a larger process.
• Various minor code cleanups and some tiny efficiency improvements.

3.2.0

• Implemented line tolerance algorithm 6 which can produce better results in certain rare cases. The default is algorithm 5.
• Fixed a bug that meant that navigating to the very first page using the global keyboard shortcut (F5) didn't work.
• Slightly improved the 3.1.3 bug fix by making it more general.

3.1.3

• Fixed a subtle bug that resulted in highlighting being painted in the wrong places in very rare cases.

3.1.2

• Added global keyboard shortcuts for navigating to the previous (F5) or next (F6) different pair of pages.
• Fixed a minor bug in the Register window.

3.1.1

• Added support for using the old or new renderer for viewing pages and for visual (i.e., PDF) reports, since in some rare cases the old renderer is better than the new one.

3.1.0

• DiffPDF now uses a much better PDF rendering library that produces clearer and sharper PNG and PDF reports. This also fixes a rare bug where some images were rendered as black rectangles.
• Added support for highlighting modes when doing Appearance comparisons.
• Added report options to allow PDF reports to output both pairs of pages (the default, and what all previous versions do), or to output only the first or second PDF's pages.
• Removed the Advanced tab and replaced it with an Appearance Mode tab and a Text Modes tab which between them have all the advanced options.

3.0.2

• Increased the experimental Pairs limit to 1000 for those with extremely powerful computers.
• Cosmetic improvement to the appearance of the splitter controls.
• Minor cosmetic improvement to how processing time is displayed.

3.0.1

• Fixed a bug that meant in rare cases a valid registration key was treated as invalid in the Register window. (A workaround for older versions is to delete the last character of the name and then retype it.)

3.0.0

• First public release of this DiffPDF 2 successor. DiffPDF 2 uses a single core no matter how many the computer has, whereas DiffPDF 3 uses all available cores. This means that DiffPDF 3 is as fast on dual core computers and faster on quad core or better computers. Furthermore DiffPDF 3 can highlight insertions, deletions, and replacements (as well as do the plain difference highlighting that DiffPDF 2 does), and DiffPDF 3 uses a more sophisticated text comparison algorithm that produces fewer false positives. DiffPDF 3 also offers more reporting options and uses the same PDF comparison engine as the command line diffpdfc tool.

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