Redact PDF

The classic mistake: open a PDF, draw black rectangles over sensitive text, save, send. The recipient opens it in their viewer, selects the redacted region, copies — and gets the original text, because the black rectangle was just an annotation on top.

This has burned governments and law firms repeatedly. The fix is to bake the redaction into the page content and discard the underlying text streams. That's what proper redaction does.

SwissArmyPDF's redactor takes the second approach: when you apply redactions, the affected pages are re-rasterized (turned into images with the black bars permanently drawn). The original text is gone from the file — not hidden, gone. The output file is also smaller as a side effect, since text streams are removed.

1. Open Redact PDF.
2. Drop your PDF onto the page.
3. Drag rectangles over content you want to hide. Add as many as you need across as many pages as you need.
4. Click Apply. Pages with redactions are re-rasterized; the hidden content is gone from the file.
5. Download the redacted PDF.

Once applied, redactions are not reversible. Always keep the original — we never modify it, but the redacted output is one-way.

• PII — Social Security numbers, dates of birth, addresses, account numbers.
• Signatures and IDs — image scans of driver's licenses, passport photos, signature bitmaps.
• Internal-only content — internal classifications, draft watermarks, employee names, internal pricing.
• Confidential clauses in a contract being shared with a non-party.
• Bank account / routing numbers on financial statements being shared with a third party.
• Witness names in legal documents before public filing.

After redacting, you should never have to trust the tool — verify. Three steps:

1. Open the redacted PDF in a different viewer. Acrobat, Preview, Chrome, Firefox.
2. Try to select the redacted region. If it lets you select text, you got an annotation-based redaction (bad). If selection fails or selects only the surrounding text, the redaction baked into the page.
3. Search the redacted file for the sensitive string. If search finds nothing, the text is gone. If search highlights inside the black rectangle, the text is still there.

SwissArmyPDF's redaction passes both checks: re-rasterized pages don't have selectable text under the black bars, and search finds nothing.

• Page text becomes images. Re-rasterized pages no longer have a selectable text layer. Search won't work on them; copy-paste won't work either. This is unavoidable for proper redaction.
• Pages without redactions are untouched. Only pages with at least one redaction rectangle get re-rasterized. The rest stay as vector PDF with searchable text.
• Image quality. Re-rasterization happens at a high default DPI (150) so visual quality stays close to original.
• File size may grow slightly if the source had heavily-compressed text streams — images take more bytes than text.

SwissArmyPDF v1 supports manual redaction — you draw rectangles. Automatic text-matching ("redact all instances of this SSN") isn't in this version.

For high-volume regex-based redaction (medical records de-identification, batch contract scrubbing), tools like Adobe Acrobat Pro, PDF-XChange, or commercial OCR pipelines are better fits. For one-off documents, manual is faster and lower-risk: you see exactly what's being redacted before applying.

• The redacted region looks transparent. You drew a rectangle but didn't click Apply. Apply is the step that bakes the redaction into the page.
• Output is missing pages. You probably had an overlay error during applying. Try with smaller redactions per pass, or update your browser.
• Lost searchability. Expected — only pages with redactions become images. Unredacted pages stay searchable.
• Black bars are misaligned. Page rotation can shift coordinates. Run through Rotate PDF first to normalize page orientation.

Redaction is specifically a privacy operation — you're trying to hide something. Uploading the un-redacted file to a third-party server to perform redaction defeats the entire point. That source file, with the sensitive content still visible, briefly existed on someone else's disk. Their breach is your breach.

SwissArmyPDF runs redaction entirely in your browser using pdfjs-dist (for rendering) and pdf-lib (for assembling the output). The un-redacted source never leaves your device. Verify in DevTools — no outbound traffic during redaction.

• Flatten PDF — finalize the redacted file (already flat for redacted pages, but flattens any remaining form fields).
• Compress PDF — re-rasterized pages compress further.
• Watermark PDF — mark the redacted version as PUBLIC or REDACTED.
• Merge PDF — combine redacted sections with new content.