How to Redact a PDF Properly (and Why Black Boxes Fail)

A PDF page is built in layers. When you draw a shape over text in most editors, or use a black highlighter, you add a new layer on top, while the original text stays in the file underneath. It is invisible on screen but still there for copying, searching, screen readers, search engines and any tool that reads the text layer.

The same applies to white rectangles used to hide text, to cropping pages, and to changing text color to black on black. None of these remove anything.

1. 1

   Open the PDF in Edit PDF

   Go to Edit PDF and open your document. It stays in your browser; nothing is uploaded.

2. 2

   Draw Redact boxes

   Choose Redact and drag a box over each piece of sensitive information. Cover the full text, including any label that would give it away.

3. 3

   Download

   When you download, everything under the boxes is permanently removed. Pages with redactions are saved as high-resolution images so nothing underneath survives, while all other pages keep their original, selectable text.

4. 4

   Verify

   Run the redacted file through Extract Text from PDF or try selecting text on the redacted pages. The removed words should not appear anywhere.

Hidden text under boxes is the famous failure, but it is not the only place information hides:

• Search the whole document for the name or number you are removing; it often appears more than once, including headers and footers.
• Check document properties (title, author, subject) in your PDF reader; they can contain names or file paths.
• Look for comments, annotations and form fields, which can hold text of their own.
• Mind the file name. A redacted file called smith-divorce-settlement.pdf has not hidden much.
• Keep the unredacted original somewhere safe and share only the redacted copy.

Before sharing a document outside your organization, look for:

• Account, card, policy and national ID numbers.
• Home addresses, phone numbers and email addresses, especially of people other than you.
• Signatures, which can be copied onto other documents.
• Salaries, prices and other figures covered by confidentiality agreements.
• Faces, number plates and other identifying details in photos embedded in the PDF.

Edit PDF also has a Whiteout tool, which covers content with a background-colored patch so you can type something new on top. That is for corrections, not secrets: like a black box, it hides content visually without removing it. Whenever information must not be recoverable, use Redact.