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Reading two versions of a long document side by side is slow, and the one sentence that matters is easy to miss. Compare PDF reads the text of both files and shows every word that was added or removed, page by page, with a few words of context around each change.
When it helps
- A lease or rental contract that comes back with “minor updates.”
- A job offer, contract or terms where one word can change your obligations: “may” becoming “must.”
- A syllabus or assignment brief your instructor updated after the first week.
- Your own drafts, when you no longer remember what you changed between version 3 and version 4.
How to compare two PDFs
- Open Compare PDF.
- Add the old version first, then the new one. Drop both PDFs into the box or click to choose them. The tool shows which file it treats as old and which as new. Got them the wrong way round? Click Swap order.
- Click Compare PDFs. The tool reads the text of both files and looks for differences. A password-protected PDF asks for its password first.
- Read the result below the tool. Removed text is struck through, added text is underlined. Each changed page of the new version has its own section, and the summary tells you how many words were added and removed.
- Jump from change to change. Use Previous change and Next change, so you don’t miss one on a long document.
- Download the report if you want to keep it. Download report saves every change as one HTML file that opens in any browser. You can print it or save it as a PDF from there.
What it compares, and what it doesn’t
Compare PDF compares the text, word by word, across the whole document. So it still finds changes when pages were added or removed; when page numbers shifted, the heading also tells you the page in the old version. Text that was moved somewhere else shows up as removed in one place and added in another. Spaces and line breaks don’t count as changes; capital letters and punctuation do.
It doesn’t compare images, layout, fonts or colors. A changed logo or a moved table cell isn’t reported, only the words.
Is one of the files a scan?
A scan is a picture of text, so there are no words to compare. The tool tells you it found no text. Run the scan through OCR PDF first to add a searchable text layer, then compare the result. Check the changes it finds against the scan, because text recognition can misread a letter.
Comparing happens in your browser, so neither file is uploaded to a server. That matters with a contract that has your name, address and salary in it. Verify that no PDF is uploaded explains how to check it yourself.
Compare PDF shows you what changed in the text. Whether those changes are acceptable is up to you; for legal questions about a contract, ask someone qualified.
Frequently asked questions
Does it find changes in images or formatting?
No. Compare PDF compares the text, word by word. Changes in pictures, layout, fonts or colors aren’t reported.
What if a page was added or removed?
The text of both documents is compared as one stream, so added and removed pages are handled. A changed page is shown with its page number in the new version, and when page numbers shifted, also its page in the old version. Text moved elsewhere shows as removed in one place and added in another.
Can I compare a scanned PDF?
Not directly: a scan has no text to compare. Add a text layer first with OCR PDF, then compare. Check the result against the scan, because recognition can misread letters.
Are my PDFs uploaded to compare them?
No. Comparing happens in your browser, so your files aren’t uploaded to a server. You can check it yourself in your browser’s network tab.