How to compare two versions of a PDF and find every change

The other side sends the contract back with a note: "Just a couple of small changes." Maybe that's true. Maybe a payment term also moved from 30 to 60 days on page 9. Reading two versions line by line is slow, and it's easy to miss things. A comparison tool does the spotting for you, so you can spend your time on what the changes mean.

Get the two files ready

A comparison is only as useful as the two files you feed it. A minute of preparation saves confusion later.

• Use the right pair. Compare the version you last sent with the version that came back, not an older draft from your downloads folder.
• Name them clearly. "proposal-v3-sent.pdf" and "proposal-v4-returned.pdf" make it obvious which side is which.
• Compare like with like. If you only have one version as a Word file, export it to PDF first, so both sides are PDFs.
• Keep the full documents. Comparing a 12-page original with a 10-page extract will flag the missing pages as removed text.

How to compare two PDFs with Pagestro

Compare PDF reads both files in your browser. Neither version is uploaded, which matters when the documents are contracts, offers or policies. It's free, with no sign-up.

Step 1. Open Compare PDF and add the original version.

Step 2. Add the new version. Both open side by side, and the comparison runs right away.

Step 3. Read the change report. It lists every change, grouped by page, with the old and new wording. Click a change to jump to it on the page.

Step 4. Download a marked copy if you need one: the new version with each change outlined in red.

Synced scrolling and shared zoom keep the two versions lined up while you read. You can also filter the report by a word, such as "fee" or "termination", to check the clauses you care about most.

Comparing means reading two pages and a list of changes at once, so it works best on a laptop, a desktop or a tablet held sideways.

What a comparison finds

Compare PDF looks at the text on every page and reports four kinds of change:

• Edited text, with the old and new wording side by side
• Added text that wasn't there before
• Removed text
• Moved text: text that stayed the same but shifted, such as paragraphs pushed down by a new clause, grouped into one change that says how far it moved

That last one matters. Without it, one new paragraph near the start can make everything after it look changed, and the real edits get lost in the noise.

What it doesn't find

Knowing the limits is part of using any comparison tool well:

• Images, colours and fonts. Changes to pictures, logos, colours or font styles aren't reported. A swapped logo or a changed signature image won't show up.
• Added or removed pages. Pages are compared in order: page 1 with page 1, page 2 with page 2. If the new version gains or loses a whole page, text after that point may show as removed on one side and added on the other.
• What a change means. A tool can show you that "may" became "must". Only you can decide whether that matters.

Comparing scanned PDFs

A scanned page has no real text, only a picture of it. Compare PDF handles this with OCR: any page with little or no text is read automatically, on both files. If the results look thin, press Deep Scan to run OCR on every page.

Recognition inside Compare PDF is in English. For documents in other languages, make each scan searchable first with OCR PDF, which reads several European languages as well as Chinese, Japanese and Korean, and then compare the searchable copies. Our guide on making a scanned PDF searchable walks through that step.

OCR is good, but not perfect. A smudge can make one digit look like another. On scanned contracts, check every flagged number against the page itself.

A review routine for contracts and drafts

Step 1. Compare the right two files: the last version you sent and the version that came back. Not an older draft.

Step 2. Read every item in the change report. Don't skip the small ones. A single word can change who is responsible for what.

Step 3. Filter the report for the terms that matter most to you: price, fee, payment, date, term, termination, liability, notice.

Step 4. Check what the tool can't see: images, the signature page, and any schedules or attachments sent as separate files.

Step 5. Send your questions back with the marked copy, so the other side sees exactly which changes you mean.

If you're not sure what to look for in the first place, our freelance contract checklist is a good companion. And once you're happy with the final version, see how to sign a PDF online.

This is general information, not legal advice. For contracts with real money or risk involved, have a lawyer review the changes.

Other ways people use it

• Editors and teachers see what a writer or student changed between two submissions.
• Employees check what's new in this year's handbook before signing that they've read it.
• Small businesses spot changed prices or quantities between two versions of a supplier's quote.

When another approach is better

• You have the editable source files. If both versions exist as Word documents, Word's Compare Documents feature shows the differences as revision marks in the document itself (Microsoft).
• The change is visual. For drawings, designs or brochures where layout and images matter more than words, compare the pages by eye at the same zoom, or use a tool built for visual comparison.

Frequently asked questions

How do I compare two PDF files for differences?

Add the original and the new version to Compare PDF. You see them side by side, with every change highlighted on the page and listed in a report.

Does it work with scanned PDFs?

Yes. Pages with little or no text are read with OCR automatically, and Deep Scan runs OCR on every page. Recognition is in English.

Does it detect changes to images or fonts?

No. It compares text, including text that moved. Changes to images, colours and fonts aren't reported.

Are my files uploaded?

No. Both PDFs are read and compared in your browser, and they never leave your device.

Can I save the comparison?

Yes. Download the marked PDF: the new version with every change outlined in red.