Redact a PDF: really remove the text, on your PC
Last updated : 2026-11-04
Redacting a PDF means removing the text from the file, not covering it: a black rectangle over a name often leaves the name in the PDF, readable by copy-paste or search.
Why a black box is not enough
A PDF stacks layers. A rectangle drawn over a text does not delete that text, it hides it on screen. Anyone who opens the file can select, copy or search it. The file properties (author, title) and any comments can also contain names.
The paradox of online services
Many tools ask you to upload the PDF to redact it. To protect personal data, you then send it to a third party. Before using an online service, read its privacy policy and check whether processing happens in your browser or on its servers.
With ndaact.ai
ndaact.ai detects names, addresses and identifiers on your PC. For a PDF that contains text, it removes that text from the file and puts a marker such as {{PERSON_a1b2}} in its place. The original PDF stays with you. The table that links each marker to its value stays on your computer. ndaact.ai does not offer to restore a redacted PDF to its original state: keep the original.
What you still need to check
- Only detected entities are replaced. An entity that is not detected stays in the clear.
- A scanned PDF is refused: it is an image with no usable text, and ndaact.ai has no OCR. The document is not sent.
- ndaact.ai does not clean the file properties. Check the author and title in the PDF properties.
- Reopen the final PDF: search for a known name and try to copy the text around the marker.
ndaact.ai is an aid, not a guarantee. For the difference between anonymisation and pseudonymisation, see the guide on definitions. For other formats (Word, Excel, PowerPoint), see anonymising a document.
Frequently asked questions
Can a scanned PDF be redacted? Not with ndaact.ai: it refuses the file rather than send it unprotected.
Is the redacted PDF anonymous? ndaact.ai performs client-side pseudonymisation. The legal qualification depends on the recipient and the context.
Can you go back to the original PDF? No, keep the original on your PC.