Compare PDF
See exactly what changed between two versions of a document: both files side by side, matching words in green, every difference in red, and a report you can download.
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Compare two PDF versions and find every change
A revised contract comes back from the other side and somewhere in forty pages a clause has moved, a number has changed and a sentence has quietly disappeared. Reading both documents in parallel is slow and unreliable, because the eye skips exactly the small substitutions that matter most: a 30 that became a 60, an and that became an or.
Comparing at word level rather than by page is what makes this dependable. Inserting one sentence on page three pushes every subsequent paragraph down, and a tool that compares page images would then report the entire rest of the document as changed. Aligning the text instead means a single edit is reported as a single edit, however much it shifted the pages around it.
The result opens as two panels, the original on the left and the revised file on the right, with matching words marked green and every difference marked red, so one glance shows where the two versions part ways. A downloadable report carries the same spreads plus a summary page listing every change in one place. One thing it will not catch is a change that is not text: a replaced logo, a different shade of a table header, a redrawn chart. If the visual design is what you need to verify, that still needs eyes on both files.
Simple, practical guidance
How to use Compare PDF
Both documents are read and their text is compared word by word, so a change is found by what it says rather than where it sits. The result opens on the page with the two versions side by side: matching words in green, differences in red, and a report you can download. If the two files match, it says so instead of leaving you guessing.
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Upload the original PDF.
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Add the revised PDF.
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Run the comparison.
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Review the two versions side by side, then download the report if you need it.
Get a better result
Comparing at word level means edits are caught even when a paragraph has reflowed onto a different page, which is where a visual page by page comparison usually fails.
Know how your file is handled
Comparison runs on our server, since aligning two documents and generating a report needs tooling unavailable in a browser. Both files are deleted once the report has been produced.
Check before you share
Both PDFs need a real text layer, so scans must go through OCR first. Changes to images, colours, fonts or layout alone are not detected, because only the text is compared.
Questions people ask
Compare PDF FAQ
What counts as a change, reflowed pages, scanned documents, and reading the report.
How do I compare two PDF files?
Upload the original document, add the revised one, run the comparison, then download the report and work through the highlighted changes and the summary page.
What kinds of change does it find?
Text changes: words and sentences that were added, removed or altered. Because the comparison is word by word, a single substituted number or a changed conjunction is reported precisely.
Does it work if the pages have shifted?
Yes, and this is the main reason to compare text rather than page images. An inserted paragraph moves everything after it, but aligning the text means only the real edit is reported.
Can I compare scanned documents?
Not until they have a text layer, because there is nothing to compare otherwise. Run OCR PDF on both files first and then compare the searchable versions. OCR PDF
Will it detect a changed image or logo?
No. Only text is compared, so a replaced picture, a different colour or a redrawn chart is not reported. Those differences still need a visual check.
What does the report look like?
The two versions are shown side by side with the differences marked, and a summary page lists every change together so you can see the full picture before going into the detail.
Are my documents uploaded?
Yes. Aligning two documents and generating a report needs server side tooling, so both files are processed there over a secure connection and removed once the report is ready.
Can I compare documents with different page counts?
Yes. The comparison follows the text rather than pairing page one with page one, so a revision that added or removed pages is handled correctly.
Does formatting count as a change?
Not on its own. Making a word bold or changing its font is a presentation change rather than a text change, so it is not flagged. The words themselves are what is compared.
Is there a size limit?
Long documents take longer, since both files have to be read and aligned in full. For very large reports, comparing the relevant chapters separately is faster and easier to review.