How to redact a PDF (and why black boxes often fail)
Published
Every year, court filings and government reports leak names and numbers that were "blacked out". The text was covered, not removed, and anyone could copy it from underneath. Here is how to redact so the information is really gone.
Why a black box is not enough
A PDF is made of layers. Drawing a black shape adds a new layer on top, but the original text is still in the file. Select the area, copy and paste, and the hidden words appear. Search engines and screen readers can find them too.
Changing the text colour to black, adding a highlight, or covering it with an image all have the same problem.
What real redaction does
Proper redaction removes the content under each box from the file itself. Our Redact PDF tool does this by redrawing every page that has a box as a flat image with the box burnt in, so the text, pictures and links underneath no longer exist. It also removes document metadata and links that could point back to removed content.
Step by step
- Open Redact PDF and add your document.
- Drag a box over each name, number or picture to remove, on every page where it appears.
- Press Redact permanently and download the result.
- Check it: try selecting and copying the redacted areas, and search for the removed words.
Do not forget the hidden places
Sensitive details also hide in file names, document properties, comments and attachments. Rename the file, and use Edit metadata to clear the author and title before sharing.