"I only changed a couple of words" is easy to say and hard to check. When a contract comes back from the other side, a colleague returns a revised report, or the printer sends a new proof, reading two versions next to each other is slow and unreliable. The S-PDF compare PDF tool does it for you: upload the original and the changed version, and it shows what is different, both in the text and visually on each page.
You get a text similarity percentage for a quick sense of how much has changed, a list of every changed line with its page number, and a side-by-side view of the pages with the changed areas highlighted. Everything can be downloaded as a report to keep or send on.
How to compare two PDF files
- Add the original Drop the earlier version of the document into the first box, labelled as the original.
- Add the changed version Drop the newer version into the second box. Keeping the order right means removed and added content are labelled correctly.
- Review the differences Check the similarity percentage, read through the list of text changes, and look at the highlighted page previews side by side.
- Download the report Download a ZIP with a comparison report PDF and a text file that lists every change.
Why use S-PDF for Compare PDF
- Similarity scoreA percentage tells you at a glance whether you are looking at a few edits or a heavy rewrite.
- Every text change listedRemoved lines appear in red and added lines in blue, each with the page number where it occurs.
- Visual page comparisonPages are shown side by side with changed areas highlighted, red on the original and blue on the new version.
- Report you can shareThe comparison report PDF puts both versions side by side with the highlights included.
- Plain-text change listA text file lists every change, handy for pasting into an email, a ticket or a review note.
- Nothing to installWorks in any modern browser on Windows, Mac, Linux, Chromebook, iPhone, iPad and Android.
How to read the results
| Result | What it shows | Use it to |
|---|---|---|
| Similarity percentage | How much of the text is the same in both versions | Decide quickly whether a full review is needed |
| Text changes | Removed lines in red, added lines in blue, with page numbers | Check wording, numbers, dates and names line by line |
| Visual comparison | Each page side by side, changed areas highlighted | Catch moved images, new logos, layout and formatting changes |
The text is compared in full, however long the document. The visual side-by-side comparison covers the first 60 pages. A changed word typically shows up as one removed line and one added line, so compare the red and blue lines next to each other to see exactly which word changed.
When comparing PDFs saves the most time
- Contracts and redlines. The other party sends back a "clean" PDF. Compare it with the version you sent to make sure nothing changed that wasn't discussed, from a payment term to a notice period.
- Checking a colleague's edits. When someone revises a policy, a report or a proposal, see their changes without asking them to list them.
- Print proofs. Compare the printer's proof with your approved file and spot a shifted image, a missing line or a changed price before the run.
- Version control. Keep track of what changed between v3 and v4 of a manual or a tender document, and attach the report to your records.
Limitations and how to work around them
Scanned PDFs have no text to compare. A scan is a picture of a page, so the text comparison has nothing to read. The visual comparison still works. For a text comparison, run both files through OCR PDF first. Keep in mind that OCR can misread a character here and there, which may show up as small differences.
Big layout changes create a lot of noise. If the new version uses a different font size, margins or page size, the text reflows and lines break in different places. The comparison then reports many changed lines even where the wording is the same. Comparing files exported from the same template gives the cleanest results.
Comparing sections of long documents. To focus on one chapter, use Extract pages on both versions and compare just those parts. That also keeps the whole section inside the 60-page visual comparison.
Frequently asked questions
How do I compare two PDF files for differences?
Upload the original version in the first box and the changed version in the second. The tool shows a similarity percentage, a list of removed and added lines with page numbers, and a highlighted side-by-side view of the pages.
What do the red and blue highlights mean?
Red marks content that was removed and appears on the original. Blue marks content that was added and appears on the new version. The same colours are used in the text list and the page previews.
Is there a page limit?
The text of both documents is compared in full. The visual side-by-side comparison covers the first 60 pages.
Can I compare scanned PDFs?
The visual comparison works on scans. The text comparison needs real text, so run both scans through OCR PDF first if you want a list of text changes.
What is included in the download?
A ZIP containing a comparison report PDF, with both versions side by side and the highlights included, and a text file listing every change.
Why does it show so many changes when only a few words changed?
If the layout changed, for example a new font, margin or page size, lines break in different places and many lines are reported as changed. Comparing versions that share the same layout gives the clearest results.
Is it free to compare PDF files?
Yes. You can run 5 comparisons a day with up to 50 MB per task, with no signup and no watermark. Pro ($5 a month or $50 a year) allows 500 MB per task, unlimited tasks under fair use, and no ads.
Are the documents I compare kept private?
Yes. Both files travel over HTTPS, are stored privately, never shared or reused, and are deleted automatically one hour after your last action, or immediately with Delete my files now.
Last updated by The S-PDF team.