I want to compare two PDF files and show the differences.

The application must

  • be gratis
  • run on Windows (10 at least, 7 appreciated)
  • compare the text that is contained in those PDFs
  • visually highlight the changes found

I don't need

  • comparison of the images contained in the PDF

I don't want

  • visual comparison, such as using ImageMagick or pyPdfCompare(which were suggested in one of the linked answers)
  • trials or free versions that can open PDFs limited in size, such as DiffNow (which was suggested in one of the linked answers). I have documents that are 20 MB or larger.

The PDFs in question are in general similar with respect to text. I expect only little changes. However, visual comparison is not possible, since adding a sentence may move all subsequent content to a new page.

I have tried:

  • copy/pasting the text of the PDF and using a Diff-Tool like Winmerge. However, that resulted in issues with special characters such as ß and also with line breaks. Also, in the end it's hard to find out on which page that difference is.
  • the question Free PDF comparison tool, but it has been asked for OS X and I need it for Windows. I have tried some of the tools that work on Windows as well,

3 Answers 3


diffpdf (version 2)

diffpdf is premium software from version 3 onward, but version 2 is still gratis.

  • Gratis
  • Runs on Windows
  • Compare PDFs side-by-side in a GUI with highlighting
  • Synchronized scrolling
  • Portable app - no installation required

Available at https://portableapps.com/apps/utilities/diffpdf_portable

Screenshot of diffpdf comparing two files and highlighting changes in pink

Note: Diffpdf compares the PDFs page-by-page, so it won't work as well if the changes have moved a paragraph to a different page. There's a couple ways to work around this:

  1. You can specify which pairs of pages to compare. For example, if a paragraph has moved from page 2 to page 3 in the new version of the file, compare page 2 with page 3 in order to compare that paragraph.

Shows comparing page 4 of one document to page 5 of a different document

  1. You can use this bash script to convert both PDFs to a single-page "scroll" before comparing them. (You can run bash scripts on Windows 10 using wsl.exe)

What about diffpdf It uses text highlighting and runs on both windows and linux environment.

From softpedia:

Differences between the two PDF items can be noticed by viewing their content, since they are highlighted in red, according to the comparison type of your choosing.

But I am not fully sure that it is completly gratis.

  • 3
    Sorry, it's not gratis, it just has a 20 days trial period. Commented Sep 3, 2018 at 15:00

I'm currently adding pdf support to my diff. Its not free but fairly cheap at $19. I have it working with some test pdf's but if you want to try it with your pdf's please contact the support email on my site and I can make it available to you. See AJC Diff

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