How to Redact a PDF Properly (and Why Black Boxes Often Fail)
Drawing a black rectangle over text does not remove it. Here is how real redaction works and how to check that it worked.
· 5 min read
Every year there is another story about a court filing or government report where the "blacked out" names could be read by simply copying the text. The cause is almost always the same: someone drew a black shape over the text instead of redacting it.
Covering is not removing
A PDF is built in layers. When you draw a rectangle with a highlighter or shape tool, you add a new layer on top. The words underneath are still in the file. Anyone can:
- Select the area and copy the text into a text editor
- Use search (Ctrl+F) to find the "hidden" words
- Delete the rectangle in any PDF editor
The same goes for changing the text colour to black or white. It looks hidden; it is not.
What real redaction does
Proper redaction deletes the content in the marked area and then draws the black box to show where something was removed. After saving, the original words no longer exist in the file.
Redact PDF works this way: you draw boxes over names, ID numbers, card numbers or signatures, and each redacted page is flattened into an image with the boxes burned in. The text underneath is gone, so it cannot be selected, searched or recovered.
A safe redaction routine
- Work on a copy. Redaction cannot be undone, which is the point.
- Search for every occurrence. A name on page 1 often appears again in a footer or on page 14.
- Do not forget images. A scanned signature or a photo of an ID card is an image; cover it fully.
- Check the metadata. The author field or document title can still contain what you removed from the page. Clean it with Edit PDF Metadata.
- Verify. Open the result, press Ctrl+F and search for a redacted word. Try selecting the black area and pasting it somewhere. If nothing comes out, you are done.
What to redact before sending
- National ID, passport and social security numbers
- Bank account numbers, IBANs, card numbers
- Home addresses and personal phone numbers
- Signatures, when the recipient only needs to see the content
- Health information and salary figures
The whole process runs in your browser, so the sensitive original never has to be uploaded anywhere for you to clean it.
Open: Redact PDF, free, and your file never leaves your device.