The two comparison modes solve different crimes
Text comparison answers “what does this version say differently?” It extracts both documents’ text layers and diffs them like code — robust against reflowed paragraphs, font changes, and page-number shifts. Visual comparison answers “what does this version look like differently?” by overlaying rendered pages pixel by pixel — the only mode that catches image swaps, stamp additions, layout manipulation, and changes inside embedded figures. The professional habit is knowing which question you’re asking: editors and lawyers usually mean the first; auditors and fraud-checkers often need the second.
Real workflows this replaces
- Contract redline verification — counterparty returns “the same document with one agreed change”; comparison proves whether one change is really all that moved. The cases where it isn’t are exactly the cases that matter.
- Invoice and PO verification — comparing this month’s invoice against last month’s surfaces quietly-changed rates or added line items in seconds.
- Design and print proofs — confirming the printer’s final proof matches the approved artwork, catching color-profile and font-substitution drift.
- Regulatory document control — verifying that a republished policy or datasheet changed only the sections the change-log claims.
- Thesis and manuscript versions — finding what a co-author actually edited when they returned the file without tracked changes.
Preparing two PDFs for a clean comparison
Comparison quality is mostly input hygiene. Ensure both files cover the same page range (a one-page insert early in the document makes every later page “different” — if pages shifted, compare section by section). Export both from the same source application when possible: the same Word document exported once via Word and once via a print driver produces different kerning and line breaks that show up as noise. And compare final PDFs, not a PDF against its source document — conversion itself introduces differences that aren’t edits.