Why comparing PDFs matters
PDF is the format in which contracts, offers, price lists, terms and conditions and reports are sent around. When a document comes back as a new version, you usually get a short note like "we only fixed a few typos". Sometimes that is true. Sometimes a payment term moved from 30 to 60 days, a liability cap changed or a sentence that protected you is gone.
Reading two long documents side by side and spotting such edits by eye is slow and unreliable, especially when the layout changed and every page breaks at a different place. A comparison tool does the boring part: it lines up both texts and shows exactly which words differ, so you only have to read the changes.
Try it here: Compare PDF
Open the full tool pageThe fast way: compare in the browser
Drop the older version on Original PDF and the newer version on New PDF. The text of both files is read page by page and compared word by word across the whole document. Removed words are shown in red and struck through, added words are shown in green. The summary at the top says how many passages were added, removed and changed, and how many words that is in total.
Use Next change and Previous to go through the edits one by one, or open All changes to see a list in which every entry shows the type of change, the page in the original and the page in the new file. Click an entry to jump to it. Download report saves the summary and the full list as an HTML file that opens in any browser and can be printed or saved as PDF for your records.
Both files stay on your device. Nothing is uploaded, which matters for contracts, salary documents and anything else confidential.
Side by side, inline or on the page
The View setting changes how the differences are shown. Each view is useful for a different kind of check.
| View | What you see | Best for |
|---|---|---|
| Side by side | Original on the left, new version on the right, aligned line by line; unchanged parts are folded away | Long contracts and reports, reviewing every edit in context |
| Inline | One running text with deletions in red and additions in green | Short documents and quick reading of a list of edits |
| On the page | Both pages drawn as images with the changed words colored where they are | Tables, forms, price lists and layouts where the position matters |
Ignoring spaces, case and punctuation
PDFs created by different programs often differ in ways that do not matter: extra spaces, a capital letter at the start of a list item, a semicolon instead of a full stop. Three options let you hide that noise.
Ignore spaces is on by default. It means that a word that only moved to another line, or text that is spaced differently, does not count as a change. Ignore case treats Notice and notice as the same word. Ignore punctuation skips commas, full stops, brackets and similar marks, so only words and numbers are compared.
- For contracts and legal text, keep case and punctuation on. A missing comma or a capital letter can change the meaning.
- For drafts and reports that were reformatted, turn on Ignore case and Ignore punctuation to see only real word changes.
- The settings are stored in the page address, so Share with these settings gives a colleague the same view.
Comparing PDFs in Acrobat and Word
Adobe Acrobat Pro includes a Compare Files tool: open Acrobat, choose All tools > Compare Files, select the old and the new file and click Compare. It creates a report of text and image changes. The feature is part of the paid version; the free Acrobat Reader cannot compare files.
Microsoft Word can also do it in two steps. Open each PDF in Word (File > Open), which converts it into an editable document, save both as Word files, then use Review > Compare > Compare to compare the two documents. This works well for text heavy PDFs, but the conversion can shift the layout of tables and columns, and differences that come from the conversion itself may show up as changes.
A browser tool needs no installation and no subscription, and it works on any computer, including a work laptop where you cannot install software.
Scanned PDFs and other limits
A comparison works on the text inside the PDF. A scanned document is a set of pictures of pages and contains no text, so there is nothing to compare. In that case the tool says so and points you to OCR PDF, which recognizes the text and makes the file searchable. Run OCR on both scans and compare the results; check the changes it finds against the page images, because OCR can misread single letters.
Text comparison does not see formatting. A word that only became bold, a different font, a new logo or a replaced image is not reported unless the words changed too. Words split with a hyphen at the end of a line are joined back together, so a different line break does not show up as a change. Very large documents that are almost entirely different may be too much to compare at once; compare them in parts.
A checklist for contract changes
- Always compare against the version you agreed on, not against the other side's summary or tracked changes.
- Look first at numbers: amounts, percentages, dates, notice periods and deadlines.
- Check small words that flip the meaning: not, may, must, shall, only, and, or.
- Check names, addresses and company details, which are easy to swap unnoticed.
- Keep the downloaded report together with both PDFs, so you can show later what you checked.