Two ways to compare PDFs
When a contract, a quote or a policy comes back “with a few small changes”, you need to know exactly what changed. Reading both versions side by side is slow, and it is easy to miss a single altered number. This tool compares two PDFs in two complementary ways.
Text changes extracts the words from both files and lines them up with a diff algorithm, the same kind programmers use to review code. Lines that were removed are shaded red, lines that were added are green, and inside a changed line the exact words that differ are highlighted. Long stretches that did not change are folded away, so you only read what matters.
Visual overlay draws the same page of both files and compares them pixel by pixel. Anything that appears only in the changed file is painted green; anything only in the original is red; everything identical fades to light grey. This catches changes that have no text: a swapped logo, a new signature, a moved stamp, a redrawn chart or a different photo.
How to compare two PDFs
- Add the original on the left and the changed version on the right.
- Read the text changes. The summary line counts added and removed lines. Switch to Words to see a flowing view in which every changed word is marked in place. Tick “Ignore upper/lower case” if capitalisation changes do not matter to you.
- Open the visual overlay and step through the pages with the arrows. Switch between Differences, Original and Changed to look closely.
- Click “Check every page for changes” to get a list of pages with the percentage of each page that differs. Click a page to jump to it.
A worked example
A supplier sends version 2 of a 9-page service agreement. The text view shows four changes:
- clause 3.1: “30 days” became “45 days” (payment terms)
- clause 7.4: “unlimited” became “limited to the fees paid in the previous 12 months” (liability)
- a new clause 9.6 on price increases
- the date on the cover page
The visual overlay adds a fifth: on page 9 the supplier’s signature block has moved and the company stamp is different. None of these changes were mentioned in the covering email, and the liability cap is the one a lawyer would want to see.
Reading the results well
- Reflow is normal. If a paragraph on page 2 grows by one line, everything after it moves down. The visual overlay of later pages will show red and green “ghosts” of the same text shifted slightly. The text view is not affected by this, so trust it for wording and use the overlay for things the text cannot show.
- Line breaks are ignored. Text is compared line by line, but blank lines and extra spaces are ignored, so a document re-exported with different spacing does not drown you in false changes.
- Different page sizes (A4 against Letter) make the overlay misalign. Compare the text instead.
- Scanned PDFs have no text to compare. The overlay still works, or you can run both files through OCR PDF first to get a text comparison.
Compare in your browser vs typical online comparison tools
| This tool | Typical online PDF comparison | |
|---|---|---|
| Files uploaded | No, both stay on your device | Yes, usually both versions |
| Text and visual comparison | Both, free | Often one is a paid feature |
| Page or file limits | None | Common on free plans |
| Account needed | No | Often |
Comparing drafts usually means handling confidential terms, prices and personal data. Uploading two versions of the same contract doubles that exposure, so keeping both files on your device is a real advantage here.
Related tools
To compare plain text, such as two versions of an email or a snippet copied from a website, use Text Compare. To pull all the text out of a PDF and read it in full, use PDF to Text. If you need to send back an annotated copy, mark the changes with highlights and comments in Edit PDF.