How to redact a PDF properly

Real redaction removes the hidden text, not just the way it looks. Drawing a black rectangle over words leaves the words in the file, where anyone can still select and copy them. Flattening the page to an image removes them.

Many people cover text with a black shape in a PDF editor and share the file. The text is still there underneath. Press Ctrl+A, copy, and paste into a text editor, and the “hidden” words appear.

You type the words or patterns to hide, one per line. The tool finds each match, covers it with a black box, and saves every page as a picture. With no text layer left, nothing can be copied out of the result.

Open the finished file and read every page. Text inside images, or a name split across two lines, may not be matched. Add those words to the list and run it again.

Redacting the page does not touch document properties. Run “Clean & edit properties” to remove the author, software and any hidden metadata, and use “Inspect a PDF” to see what is stored.