How to redact text in a PDF so it cannot be read

Redacting a PDF with a black rectangle is the most repeated mistake in public bodies and law firms. The shape is drawn on top of the text, but the text remains in the file: select it, copy it, or open the PDF in another viewer and you can read everything.

Why a black box is not redaction

A PDF stores independent layers. Drawing an opaque shape adds a graphic layer; it does not delete the text layer.

How to redact properly

1. Mark the content to remove (names, ID numbers, addresses, phones, IBANs, plates).
2. Apply true redaction, which deletes the characters from the file.
3. Flatten and save as a new file.
4. Strip the metadata (author, title, comments).
5. Verify: try to copy the redacted area and search the name with Ctrl+F.

If the PDF is a scan

Then the text is an image. You need OCR to locate the data and must delete the image fragment, not just paint over it — otherwise the OCR layer keeps the data searchable.

What to redact in a public document

• Names of third parties with no public role.
• ID and social security numbers, personal case references.
• Private addresses, phone numbers and emails.
• IBANs, individual amounts and property records.
• Health data, minors, victims and whistleblowers.

Automate it

anonimizia detects personal data automatically, applies true redaction or masking (or pseudonymises with codes and tokens when you still need the data) and returns the final PDF with a report of everything removed.