How to check if two PDF files are different
Sometimes you need to know whether two PDF files — a draft and a revised version, or an original and a scan — are actually the same or have been changed.
Quick checks
- File size — a different size is a first signal something changed, though not proof.
- Page count — open both and check they have the same number of pages.
- Side-by-side viewing — open both in separate windows or tabs and scroll through together.
For text-based documents
If both files are text-based (not scans), convert each to Word using PDF to Word and use a word processor's "compare documents" feature, which highlights exact differences.
For a definitive check
Generate a hash for each file using Hash Generator — if the hashes match exactly, the files are byte-for-byte identical. If they differ even slightly, so do the hashes, though this doesn't show what changed, only that something did.
A practical middle ground
For most everyday cases — checking whether a supplier sent an updated quote, or whether a contract draft changed — opening both files side by side and scrolling through together catches the differences that matter without needing specialised comparison software.
When precision matters
For legal or contractual documents where an exact, provable difference matters, converting both to Word with PDF to Word and using a word processor's built-in compare feature gives a documented, highlighted list of every change — far more reliable than eyeballing two PDFs.
Documenting what you find
For anything with legal or contractual weight, note down the specific differences you find in writing as you go, rather than relying on memory after finishing a side-by-side review — this creates a record if the comparison needs to be referenced later.
