Compare PDF Files Online
Review revisions, proofreading changes, and version differences in PDF documents with DiffQuery.
How online PDF comparison works
DiffQuery extracts the text layer from each PDF, aligns the two documents page by page, and highlights every insertion and deletion in place. Repeated elements such as headers, footers, and page numbers are part of the extracted text, so treat a change that appears on every page as layout noise unless the text itself matters.
Compare two PDF files in three steps
Open the PDF comparison tool, drop the older and the newer file into the left and right panels, and press compare. The merged view shows removed text in one color and added text in another, so you can scan a full contract in minutes instead of switching windows.
Typical PDF comparison scenarios
Review contract redlines before signing, check that a revised quote or invoice only changes what it should, verify a thesis or report draft after supervisor edits, and confirm the final PDF matches the approved version before publication.
Related guides
PDF comparison FAQ
Can I compare scanned PDFs?
Only if the scans contain a text layer produced by OCR. Image-only scans have no extractable text, so there is nothing to diff; run OCR first and compare the resulting files.
Are my PDF files uploaded to a server?
No. Comparison runs locally in your browser, so the contents of your documents never leave your device.
Why does the same difference appear on every page?
Repeated differences usually come from layout elements such as footers, dates, page numbers, or watermarks. If the repeated text itself did not change in substance, treat it as noise.