Why look for an alternative
Acrobat Pro's Compare Files tool works well, but it is only in the paid Acrobat Pro subscription, not the free Acrobat Reader. Many people need to compare two documents a few times a month, and a full Acrobat Pro subscription for one feature is hard to justify. Teams that want to automate comparisons also need an API, which a desktop tool does not provide.
What a good alternative must do
- Compare text, not pixels, so that one inserted sentence is one change rather than every following page lighting up.
- Ignore running headers, footers and page numbers.
- Handle tables and two-column layouts without false differences.
- Report each change with its page number, and produce a redline you can send.
- Not keep your documents after the comparison.
The options
- A browser-based comparison such as the tool on this site: free for documents up to 30 pages, no install, redline PDF, side-by-side view and change list, with a REST API for automation.
- Microsoft Word Compare: free if you already have Word, but converting PDFs to Word first introduces layout differences that show up as false changes.
- Visual diff tools such as the open-source diff-pdf: good for drawings and layout, poor for text documents because reflow marks everything after an edit.
- Text extraction plus diff (pdftotext and diff): free and scriptable, but noisy without header, footer and table handling.
Which one to choose
For occasional comparisons of contracts and other text documents, a free browser tool covers what most people use Acrobat's Compare Files for. For a review team, a monthly plan costs far less than Acrobat Pro seats for everyone. For integration into a document system, use an API. Run the same two real documents through any tool you are considering and check whether it found every change you know about.
SimpleFileTools is not affiliated with Adobe. Acrobat is a trademark of Adobe.
Try it on your own documents. Upload two versions on the homepage. Documents up to 30 pages need no account, and nothing is stored.