DiffPDF is used to compare two PDF files—textually or visually.
DiffPDF can compare two PDF files. It offers three comparison modes: Words, Characters, and Appearance.
By default the comparison is of the words on each pair of pages, but comparing character by character is also supported (e.g., for logographic languages). And there's also support for comparing the pages by appearance (for example, if a diagram is changed or if a paragraph is reformatted, or a font changed). It is also possible to compare particular pages or page ranges. For example, if there are two versions of a PDF file, one with pages 1-12 and the other with pages 1-13 because of an extra page having been added as page 4, they can be compared by specifying two page ranges, 1-12 for the first and 1-3, 5-13 for the second. This will make DiffPDF compare pages in the pairs (1, 1), (2, 2), (3, 3), (4, 5), (5, 6), and so on, to (12, 13). Version 1.5.0 added the ability to save a PDF file that shows the pages that differ with their differences highlighted. Version 2.0.0 added support for margin exclusion and improved dock window handling. Version 2.1.0 added support for drag and drop, bug fixes, and French and German translations.
A couple of example PDF files are provided (boson1.pdf and boson2.pdf) so that you can try it out. PDF files can be loaded from the GUI (by pressing the File #1 and File #2 buttons, or by dragging and dropping files), or by specifying them on the command line. I use the tool regularly to compare different versions of my books (which are typically 500 or more pages), e.g., comparing a first printing with a second printing, to make sure that only the pages I intended to change have actually been changed.
If you want a command line tool that just compares two PDFs and reports whether they are different (e.g., for automated testing), use comparepdf instead.
DiffPDF is licensed under the GNU General Public License v 2 open source license.
Steven Lee has built a version for Windows. It is available from his blog http://soft.rubypdf.com/software/diffpdf or from here diffpdf-2.1.2-win32-static.zip (5MB; should work fine on both 32- and 64-bit Windows; SHA1: 7d565ce677c86b63a8de9b708aad46d3cdb87c2a). Note that there's no console output (but the command line options work; see the online help for what they are).
Reference: http://www.qtrac.eu/diffpdf.html
