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How to check a PDF redaction actually worked

Updated 20 October 2026

Not sure what's hiding in your document? Check it free. It runs in your browser, so the file never leaves your computer.

Drawing a black box over text in a PDF hides it on screen, but the words are often still in the file. Anyone can copy them out, search for them, or remove the box. It's one of the most common ways confidential details leak from legal, HR and public-sector documents.

The two-minute test

Open the redacted PDF in any PDF reader.
Press Ctrl+A (Cmd+A on a Mac) to select everything, then copy.
Paste into a plain text editor, such as Notepad or TextEdit.
Read through it, or search for a word you know was redacted. If you can see it, the redaction didn't work.
Also try the reader's search box (Ctrl+F) with a redacted name or number. If it highlights a spot under a black box, the text is still there.

The free Clean Retype check does this for every page at once: it lists any text sitting under a black box and shows you the words it found.

Why redactions fail

A shape was drawn over the text. Black rectangles, highlighter set to black, or a black text background only cover the words. They don't delete them.
Redactions were marked but never applied. In Adobe Acrobat, marking text for redaction is a separate step from applying it. Until you apply, nothing is removed.
The PDF was made from a Word file with black highlighting. The words travel into the PDF exactly as they were.
Earlier versions are still inside the file. PDFs can be saved by adding changes on top, so an older, unredacted version may still be recoverable.

How to redact properly

Adobe Acrobat Pro: open Redact, mark the text, then click Apply. When asked, choose to also remove hidden information. Save as a new file.
Preview on a Mac (macOS 11 or later): use Tools › Redact rather than a drawn shape. Preview removes the text when you save.
Starting from Word: delete the confidential words in Word first, or replace them with a placeholder like [REDACTED], then make the PDF.
Test the result with the two-minute test above before you send it.

Or check it in seconds

Drop the file into the free Clean Retype check and it lists what's hiding inside: author names, comments, hidden sheets and rows, speaker notes, earlier versions, and text still sitting under black boxes.

Check a file free No sign-up

It runs in your browser, so the file never leaves your computer. Works with Word, Excel, PowerPoint and PDF files.