Guide

How to redact a PDF so it’s really gone.

Every year, sensitive information leaks from “redacted” documents because someone drew black boxes over the text. Here’s how to remove it for real, and check that it worked.

By Rohan Vijaykumar · · 5 min read

The black box mistake

A black rectangle drawn on top of text hides it from view, but the text is still in the PDF underneath. Anyone can select it, copy it, or delete the rectangle. The same goes for black highlighting and for setting text to black on a black background.

Real redaction removes the content from the page itself. After that, there’s nothing underneath to recover.

Redact a PDF with Paperwing

Paperwing is a free desktop app for Windows and Mac whose Redact tool deletes the text and graphics under each redaction. It runs on your computer, so the unredacted file never goes anywhere.

  1. Download Paperwing and open your PDF.
  2. Open All tools and choose Redact a PDF.
  3. Mark the text and areas to remove: names, account numbers, addresses, signatures, faces.
  4. Apply the redactions. The content under each mark is deleted from the page.
  5. Run Sanitize PDF to remove metadata, hidden data, attachments and scripts.
  6. Save it as a new file with Shift+Ctrl+S, and keep the original somewhere safe.

Don’t forget the hidden parts

Page content isn’t the only place information hides:

  • Metadata: the author, title, subject and keywords. Remove it with Remove Metadata or Sanitize PDF.
  • Comments and annotations: review notes often repeat the very details you redacted.
  • Bookmarks and attachments: a bookmark titled with a person’s name, or an attached original.
  • Form fields: values typed into fields. Flatten the document if it has any.
  • The text layer of scans: OCR text sits invisibly behind a scanned image. Mark it for redaction too, then search to make sure it’s gone.

Check your work

  1. Open the redacted file and press Ctrl+F. Search for a name or number you removed: it shouldn’t be found.
  2. Try selecting and copying text around each redaction, then paste it somewhere. Nothing removed should come back.
  3. Check the document properties (Ctrl+D in Paperwing) for leftover metadata.

Quick answers

Is redaction reversible? Not once it’s applied and saved. That’s the point, so keep the original.

Can I redact a scanned PDF? Mark the areas on the scan the same way. Afterwards, zoom in to confirm they’re gone, and search the file in case an OCR text layer still holds the words.

Is it safe to redact online? It means uploading the unredacted document, which defeats the purpose for sensitive files.

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