About Compare PDF
Two versions of the same document arrive in your inbox and you need to know what changed. The CEO sent the revised contract; you want to find the clause that was edited. A reviewer returned the proposal; you want to see their amendments. The vendor sent the new version of the price sheet; you want to spot the items where the price moved.
Compare PDF puts the two documents side by side so you can scroll through both at the same scroll position and see the differences page by page. It's the digital equivalent of laying both copies of a contract on the table and flicking your eyes from left to right.
How the comparison works
Drop in two PDFs. The tool renders both as scrollable previews positioned next to each other. Their scroll positions are linked, so when you scroll one, the other scrolls in sync. You're always looking at the same page of both files.
Zooming is also synced. Zoom into a section in one and the other zooms to match, which is essential when you're trying to compare detailed text or numbers.
If the documents have different page counts, the shorter one stops scrolling at its last page while the longer one continues. The view makes it clear which is which.
Where this earns its keep
Tracking contract revisions. A clean original and a marked-up redline let you find each change without depending on the redliner having used track changes properly.
Comparing draft and final versions of a proposal before signing off.
Spotting unexpected differences between a PDF you sent and the one that came back. Sometimes a recipient edits the document before signing and the changes need to be caught.
Verifying that a regenerated PDF (say, after fixing a typo) matches the original everywhere else.
Comparing two snapshots of a regulatory filing across quarters.
Limits to keep in mind
This is a visual comparison, not a textual diff. The tool shows you both documents; the actual finding of differences is on you, scanning the pages with your eyes. The advantage of visual comparison is that it catches everything: text changes, layout shifts, image swaps, anything visible. A textual diff would miss image and layout changes.
For very long documents where you suspect only a few small changes, visual comparison can be tiring. Plan a coffee break.
Privacy
Both files stay on your machine. The rendering and the side-by-side view are built in the browser. Especially important when you're comparing sensitive contracts or financial documents.
Workflow tips for long documents
Before you start, scroll quickly through both documents and note the page count. A difference in page count points you at where new content was inserted or removed. That alone can save you half the comparison time.
Open a notes app alongside the comparison window. As you spot differences, jot down the page number and a short description. Trying to keep them all in your head past about ten changes is a losing game.
For very long contracts, work in passes. First pass: scan for layout shifts and added or removed paragraphs. Second pass: zoom in on areas that looked different and read carefully. Most people miss differences in the small print on a single pass; two passes catch much more.
If you need to send the differences back to the other party, screenshot each one inside the comparison view. Your screenshot already has the two versions side by side, which is the clearest way to communicate a change.