How to redact a PDF properly (so hidden text can't be recovered)
Redact a PDF the right way for free. Find and remove names, phone numbers, PAN, Aadhaar and card numbers, or draw boxes, so the hidden text is truly gone.
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🔒 Files never leave your device
Compare PDF — See Exactly What Changed
Drop two versions of a document. Every added and removed word is highlighted, and changed areas are boxed page by page. Free and private.
📄
Original PDF
the older version
📝
Revised PDF
the newer version
Comparing…
Neither PDF has selectable text (they look scanned), so the visual comparison is shown. To compare the words too, run both through OCR PDF first.
Original:
Revised:
How do I compare two PDF files for free?
Open PDFChai’s free Compare PDF tool, drop the older file into Original and the newer file into Revised, then click Compare PDFs. The text of both is read in your browser and compared word by word: removed words are shown in red and struck through, added words in green, side by side or inline, with Previous and Next buttons to step through each change. Switch to Visual to see changed areas boxed on each page, which is ideal for drawings and scans. Neither file is uploaded.
PDFChai Compare PDF vs Other Ways to Compare
| Feature | PDFChai | Reading both versions / typical tools |
|---|---|---|
| Finding changes | Every added and removed word highlighted | Easy to miss small edits by eye |
| Moved text | Text comparison follows paragraphs across pages | Page-by-page tools flag everything after an insertion |
| Drawings & scans | Visual mode boxes changed areas | Text-only tools see nothing |
| Privacy | Both files stay on your device | Often uploaded to a server |
| Cost | Free, no signup | Often a paid or premium feature |
| Report | Print or save the comparison | Varies |
Comparison reflects common approaches and tools as of 2026 and varies by provider.
What does Compare PDF do?
When a contract, quotation, policy or thesis comes back as a new PDF, the hard part is finding what actually changed. Reading both versions line by line is slow, and a single altered number or deleted clause is easy to miss. Compare PDF does that check for you: drop in the original and the revised file and every difference is highlighted.
The text comparison reads both documents in reading order, including two-column pages, and lines them up paragraph by paragraph using the same diff algorithm that version-control systems such as Git use. Inside each changed paragraph it works word by word, so you see exactly which words were removed and which were added. Because it follows the text rather than the page, an inserted paragraph doesn't make everything after it look different. View the result side by side or inline, hide unchanged text, and jump from change to change.
The visual comparison works page by page instead. Matching pages are drawn and compared pixel by pixel, and every area that looks different is boxed in red, with an overlay mode that shows both versions on top of each other. That catches what text comparison can't see: changes in drawings, stamps, signatures, images, layout and scanned pages. Both files are processed in your browser, so confidential documents are never uploaded.
⚡ Quick Answer:
- Open debugspot.com/compare-pdf
- Drop the older file into Original
- Drop the newer file into Revised
- Click Compare PDFs
- Step through changes, or switch to Visual
100% free · No signup · No watermark · Files stay on your device
Step-by-Step Guide
Everything you need to know — done in under a minute.
1
Add both versions
Drop the earlier version into Original and the later one into Revised, or click each box to choose a file. The ⇄ button swaps them if you put them the wrong way round. Password-protected PDFs need Unlock PDF first.
2
Compare
Click Compare PDFs. Both documents are read page by page, and a summary shows how many sections changed and how many words were added and removed.
3
Review the text changes
Removed words are red and struck through; added words are green. Tick Only show changes to hide matching text, use Inline view on small screens, and use Previous and Next to move between changes. Page numbers show where each change sits in both files.
4
Check the pages visually
Open the Visual tab to see each page of the revised file with changed areas boxed. Switch a page to Original or Overlay to see exactly what moved. Print or save the comparison as a PDF report.
How Does It Work?
Understanding what happens behind the scenes helps you trust the tool — especially with confidential files.
📖 Reading both documents
pdf.js extracts the text of each page with positions, and PDF to Word's layout engine rebuilds lines and paragraphs in reading order, including two-column pages. Bare page numbers are ignored so re-pagination doesn't count as a change.
🧮 Paragraphs, then words
The Myers diff algorithm finds the smallest set of paragraph insertions and deletions. Each changed section is then compared word by word, so a single altered figure is highlighted on its own.
🖼️ Pixel comparison
For the visual check, matching pages are drawn at the same width and compared in small tiles. Tiles that differ are grouped into boxes and outlined on the page.
🔒 All in your browser
Neither file leaves your device. The comparison exists only in this tab, and you decide whether to print or save it.
Key Features & Advantages
🔍
Word-level highlights
See the exact words that were added or removed, not just which page changed.
↔️
Side by side or inline
Two columns for a desk, one column for a phone.
⏭️
Jump between changes
Previous and Next buttons, plus an only-changes filter for long documents.
🖼️
Visual mode
Changed areas boxed on every page, with original, revised and overlay views.
🖨️
Printable report
Print the comparison or save it as a PDF to share with colleagues.
🔒
Private
Compare confidential contracts and drafts without uploading them anywhere.
Who Uses This Tool?
This is one of the most common document tasks in work, study and everyday life. Here are the people who use it every day.
⚖️ Lawyers & legal teams
Check every clause changed between contract drafts before signing or sending a markup back.
🧾 Procurement & sales
Compare a supplier's revised quotation or terms with the version you agreed to.
🏗️ Architects & engineers
Use visual mode to spot changes between revisions of drawings and plans.
🎓 Students & academics
See what a supervisor changed in a thesis chapter, or compare two versions of a paper.
🏢 HR & compliance
Track changes between versions of policies, handbooks and regulatory documents.
📰 Editors & publishers
Confirm that only the agreed corrections made it into the final proof.
Common Use Cases
The everyday situations that bring people to this tool.
📑 Contract redlines
Find every changed word between the draft you sent and the one that came back.
💰 Quotes and invoices
Catch a changed price, quantity or payment term instantly.
📐 Drawing revisions
Box the parts of a plan that moved or changed between versions.
📜 Policy updates
Show staff exactly what changed in a new version of a policy.
🖨️ Final proof check
Make sure the print-ready PDF matches the approved text.
🔁 After converting
Compare a PDF before and after editing or converting to confirm nothing else changed.
How to Use It on Any Device
Works on every platform, right in the browser. Here are instructions for the most common devices.
🪟 How to compare PDFs on Windows
Open Chrome, Edge or Firefox, go to debugspot.com/compare-pdf and drop both files. No Acrobat Pro needed.
Works on: Windows 10, 11 · Chrome, Edge, Firefox
🍎 How to compare PDFs on Mac
Use Safari, Chrome or Firefox; drag both files from Finder onto the two boxes.
Works on: macOS · Safari, Chrome, Firefox
🤖 How to compare PDFs on Android
Choose both files from Files or Google Drive in Chrome, then use Inline view to read the changes on a phone screen.
Works on: Android 9+ · Chrome
📱 How to compare PDFs on iPhone / iPad
In Safari, pick each PDF from the Files app; the inline view fits a small screen best.
Works on: iOS 15+ · Safari, Chrome
💻 How to compare PDFs on Chromebook
It runs in Chrome with nothing to install.
Works on: All Chromebooks · Chrome
Tips & Best Practices
✅ Original first, revised second
Put the older version on the left so removals and additions read the right way round, or use ⇄ to swap.
✅ Use text mode for edited documents
When paragraphs were added or removed, text mode still lines the rest up; visual mode would flag everything that moved.
✅ Use visual mode for drawings and scans
Plans, forms and scanned pages have little or no text, so the pixel comparison is the right check.
✅ Scanned files? OCR first
To compare the words in scans, run both through OCR PDF and then compare the searchable copies.
✅ Focus on what changed
Tick “Only show changes” for long documents and step through them with Next.
✅ Keep a record
Use Print / save report to keep a PDF of the comparison with the documents.
Full List of Benefits
✓Compare two PDFs in seconds
✓Word-level added and removed text
✓Paragraph-aware: moved text doesn't flag everything
✓Side-by-side and inline views
✓Only-changes filter and change navigation
✓Page references for every change
✓Visual page comparison with changed areas boxed
✓Original, revised and overlay views
✓Printable comparison report
✓Runs entirely in your browser — files are never uploaded
✓Free with no signup and no page limit
✓Works on Windows, Mac, Linux, Android, iOS and Chromebook
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Frequently Asked Questions
Is Compare PDF free?
Yes. It is free to use as often as you like, with no signup, no watermark and no page limit.
Are my files uploaded?
No. Both PDFs are opened and compared in your browser. Nothing is sent to a server, which makes it safe for contracts and confidential drafts.
What is the difference between Text and Visual comparison?
Text comparison reads the words and shows exactly what was added or removed, even if text moved to another page. Visual comparison compares how each page looks and boxes changed areas, which catches changes in drawings, images, signatures and scans.
Why does visual mode flag a whole page after one insertion?
Adding a paragraph pushes everything below it down, so the pixels no longer line up. Use text comparison for edited documents; it lines up the text instead of the pages.
Does it notice formatting changes, like bold or font size?
Text comparison looks at the words. Changes of font, colour or layout show up in the visual comparison.
Can I compare scanned PDFs?
Visual comparison works on scans. To compare the words, run both files through OCR PDF first, then compare the searchable copies.
Do page numbers count as changes?
Paragraphs that are only a page number are ignored, so a document that was re-paginated doesn't show a change on every page.
Can I compare documents with different page counts?
Yes. Text comparison doesn't care about pages. In visual mode, extra pages are marked as only in the original or only in the revised file.
Can I save the comparison?
Click Print / save report and choose Save as PDF in the print dialog to keep a copy of the highlighted comparison.
Can I compare password-protected PDFs?
Unlock them first with Unlock PDF using the passwords you know.
How large can the files be?
There is no fixed limit. Very long documents depend on your device's memory, so a laptop or desktop is best for hundreds of pages.