Compare two PDFs
Find what changed between two versions of a document.
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Two questions, two comparisons
By text answers "what wording changed". It extracts the text from both documents and finds the differences, ignoring layout entirely — so a contract re-flowed onto different pages still compares cleanly, and you see only the clauses that actually moved.
This is what you want for a revised agreement, an edited report, or checking that a document you received matches the one you sent.
By layout renders both documents and compares the pages as images. It catches things text cannot: a moved logo, a changed font, different margins, an image swapped for another.
The trade-off is real. Insert one paragraph on page two and every page after it shifts, so layout comparison marks them all as different even though the wording is identical. That is why text is the default.
Scanned documents
A scan has no text layer, so text comparison finds nothing. The tool tells you rather than reporting the documents as identical — which would be exactly the wrong answer. Compare those by layout, or OCR them first.
Reading the similarity figure
The percentage is how much of the text is unchanged. A revision with a few edited clauses typically sits above 95%. Anything below about 70% usually means you are comparing two genuinely different documents rather than two versions of one.
What it does not do
It reports differences; it does not produce a marked-up document with tracked changes. For that you need the original in an editable format, where a word processor can compare properly.
Common questions
Which mode should I use?
Text for wording changes — it ignores re-flow. Layout for formatting, images and fonts.
Why does layout mode flag every page?
Inserting a paragraph shifts everything after it. The wording may be identical; the pixels are not.
Can it compare scanned documents?
Only by layout. A scan has no text layer, and the tool says so rather than reporting them as identical.
What does the similarity percentage mean?
How much of the text is unchanged. A normal revision sits above 95%.
Does it produce a tracked-changes document?
No. It reports differences. Tracked changes needs the original in an editable format.