How to compare two PDF files and see what changed

Someone sends back “the updated contract” and says only a few things changed. Reading both versions side by side to check is slow, and easy to get wrong. Comparing the two PDFs shows every change in seconds.

When to compare

• A landlord, employer or supplier sends a revised agreement.
• You want to confirm that the version you are about to sign matches the one you approved.
• Terms and conditions, a policy or a price list has been “updated”.
• Several people edited a report and you need to review what changed.

Step by step

1. Open Compare PDF.
2. Upload the Original PDF — the older, “before” version.
3. Upload the Changed PDF — the newer, “after” version.
4. Click Compare PDFs. Lines that were added, removed or changed are highlighted.
5. Optionally click Download report (.txt) to keep a record.

Reading the results

Always upload the older version as the original, so additions and removals are labelled the right way round. Pay special attention to small changes that matter a lot: amounts, dates, notice periods, “may” becoming “must”, and words like “not” added or removed.

What it does and doesn't detect

The comparison works on the text in the documents, line by line. It will not report changes to images, logos, colours or fonts, and a paragraph that only moved may appear as removed in one place and added in another. For scanned PDFs, there is no text to compare until you run both files through OCR PDF.

Comparing Word documents

If you have the two versions as Word files, convert both with Word to PDF and compare the results. Word's own Compare feature also works, but PDFs are what people actually sign and send, so comparing the PDFs checks the final versions.

After the comparison

• Mark up concerns for the other party with Annotate PDF — highlight, strike through or add arrows.
• Once you are happy, sign with Sign PDF.
• Save the .txt report together with both versions in case of a later dispute.

Common questions

Can I compare scanned documents? Yes, after running OCR on both.

Are my documents uploaded? No. The comparison runs entirely in your browser — useful for confidential contracts.