How to redact a PDF properly (and why black boxes don’t work)
Guides · Updated 12 October 2026 · By Tiago Santos
Every few months a court filing or a government report leaks names it was meant to hide. The cause is nearly always the same: someone drew black boxes over the text. The boxes cover the words on screen, but the text is still in the file, and anyone can copy it out.
Why black boxes don’t remove anything
A PDF is made of layers. When you draw a black rectangle in a PDF editor, or put a black highlight over text in Word before saving as PDF, you add a shape on top. The words underneath stay in the document. Select the area and copy, or open the file in another program, and the hidden text comes back.
Test a redacted PDF yourself
- Open the PDF and try to select the text under a black box. If you can copy something, it isn’t redacted.
- Use PDF to text on the file. If the hidden words appear in the result, they were never removed.
How to redact for real
True redaction removes the content, not just covers it. Redact PDF does this by rebuilding each marked page as a flat image with the boxes burned in, so nothing remains underneath: no text, no hidden layer. The trade-off is that text on those pages can no longer be selected or searched, which is exactly what redaction needs.
Redacting in your browser also means the unredacted original is never uploaded anywhere, which would defeat the point.
Don’t forget the hidden details
- Metadata: the author’s name, the software, edit dates and sometimes the original title stay in the file. Remove PDF metadata clears them.
- File names: “Smith-settlement-final.pdf” can give away what the document hides.
- Context: a blacked-out name next to a job title, a date and a town may still identify someone. Redact what identifies people, not just their names.