Finding what changed between two versions
Contract drafts, policy updates, reports, and manuals go through many revisions, and the question is always the same: what is different from the last one? Reading both side by side is slow and easy to get wrong. Compare PDF gives you a quick written list of the changes between two PDF versions.
How the comparison works
Upload the two versions. Your browser extracts the text of each, and that text is sent to our server and on to an AI model, which compares them and writes a report in which each item is tagged as added, removed, or modified. You can choose a style: a focused list of differences, a semantic comparison that concentrates on changes in meaning, or an overlay that also lists the passages that stayed the same.
Because the comparison is based on text, it works even when the two versions have different layouts or page counts.
Know the limits
The result is written by an AI model, not produced by an exact text-differencing algorithm, so it can overlook small changes — a single altered number, date, or word — and it can occasionally describe a change inaccurately. Only the first 15,000 characters of text from each document are compared, so long documents are only partly covered. Changes to images, charts, and formatting are not detected, and scanned PDFs have no text, so run OCR PDF first.
PDF Studio does not keep a copy of your text, but the AI service processes it; avoid comparing documents you must not share with a third party.
Using it well
Treat the report as a fast first pass that points you to where to look, then check critical clauses and figures in the documents themselves. For legally exact redlines, use the compare feature in your word processor or a dedicated document-comparison tool on the source files. To compare long documents, split both into matching sections with Split PDF and compare section by section.