How to redact a PDF properly (and why black boxes don't work)

Putting a black rectangle over your account number looks like redaction, but in most cases the number is still in the file. Anyone can copy it out in seconds.

Updated October 2026 · 5 min read

Why a black box isn't redaction

A PDF page is built in layers. The text, such as your Social Security number, sits on one layer. When you draw a black rectangle with a markup or comment tool, you add a new layer on top. The text underneath is untouched. It's still selectable, searchable and copyable, and it can be pulled out by anyone who opens the file in a different program.

This has caused real leaks: court filings, government reports and legal documents have all been published with "redacted" text that readers simply copied and pasted.

The 30-second test: did my redaction work?

1. Open the redacted PDF.
2. Press Ctrl/⌘ + F and search for a word or number you redacted.
3. Then press Ctrl/⌘ + A, copy, and paste into a plain text editor.

If the search finds it, or it appears in what you pasted, it isn't redacted. Delete that file and try again.

How to redact properly

Method 1: use a real redaction tool

Proper redaction tools delete the content under the box and then draw the box. Look for a tool that's specifically called Redact (not "highlight", "shape" or "markup") and that warns you the change is permanent. Adobe Acrobat Pro has one. It's a paid subscription.

Method 2: "print" to an image, the free workaround

1. Draw your black boxes with any tool.
2. Turn the page into an image. On many systems, you can print to PDF using a "print as image" option (in Acrobat Reader: Print → Advanced → Print as image), or take high-resolution screenshots of each page.
3. Make a new PDF from those images.

Because the result is just a picture of the page, there's no text underneath to recover. The downside is that none of the text in the file is selectable or searchable anymore, and files get bigger.

Method 3: Penwise Redact (Chrome)

Disclosure: we make Penwise.

Penwise's Redact tool does Method 2 for you automatically, and only on the pages you redact. You drag black boxes over what you want gone, and when you download, each page with a redaction is rebuilt as an image with the content removed. Other pages keep their selectable text. Penwise also rebuilds the file so the original page content isn't left behind as hidden leftover data. It runs in your browser, so the document is never uploaded. Redaction is part of Penwise Pro ($9.99 one-time).

Don't forget the hidden places

• File properties: author name, title and other metadata (File → Properties in most viewers).
• Form fields: a filled field can keep its value even if it's covered.
• Comments and attachments inside the PDF.
• The file name itself, like Smith-SSN-2026.pdf.