PDF comparison tool

Question

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,

Answer 1

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

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.

2. 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)

Answer 2

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.

Answer 3

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