How to Redact a PDF Properly (and What Not to Do)
"Redacting" a document usually means drawing a black box over a name, a number, or a paragraph before sending it out. It looks final. It isn't. A black rectangle in a PDF viewer is often just a shape sitting on top of the text — the original words are still in the file underneath, waiting for anyone who copies the text, opens it in a different viewer, or looks at the raw file.
Why black boxes and highlights fail
Most word processors and PDF tools treat a "redaction" as a visual edit, not a data edit. Draw a shape, fill it black, done — but the text layer underneath is untouched. Select-all-and-copy from a "redacted" PDF has embarrassed law firms, government agencies, and news organizations more than once: the black box hides the words on screen, but the words themselves ride along in the file. The same problem shows up with white-out text, tiny font sizes, or text pushed off the visible page — the content is still there for anyone who looks for it, and a redaction that only removes visibility isn't a redaction at all.
What real redaction requires
Proper redaction removes the underlying content, not just its appearance. That means using a tool built for it — Adobe Acrobat's Redact tool, or a government or legal-grade redaction tool — both of which delete the selected text and objects from the file itself, and can flatten the result to an image so there's no text layer left to extract at all. If you're not certain a tool actually deletes the content rather than just covering it, assume it doesn't.
Check before you send it
Whatever tool you used, the only way to know a document is actually clean is to look at what's really in the file — not what the viewer shows you. scrub reads a PDF or Word document on your device — nothing is uploaded — and lists what it finds: hidden or "vanished" text, tracked changes and comments, author metadata, embedded macros, PDF JavaScript, and data appended after the visible content. Right now scrub's PDF and Office support is scan-only — it shows you exactly what's still hiding in the file so you know what needs fixing, rather than removing it for you. For photos and plain text, scrub can clean the file directly; see our guide to checking documents for hidden data for the full list of what it looks for.
If scrub flags leftover text, comments, or metadata in a document you thought was redacted, that's your sign to go back to the source file, remove it properly with a real redaction tool, and re-export — never just add another box on top.
The short version
A black box in a PDF viewer doesn't delete anything — it just covers it up. Real redaction removes the underlying content; everything else is a screenshot waiting to happen. Check your file before you send it. Get scrub free and see what's actually inside.