Redact a PDF properly, so hidden text is really gone
Every so often a news story appears about a document where the blacked-out parts could be read by copying and pasting. The cause is always the same: a black shape was drawn on top, and the text stayed underneath. Here's how to avoid that.
Covering is not removing
A PDF keeps its text as real characters. If you draw a rectangle over a name in most editors, or highlight it in black, the characters are still there: select the area, copy, paste, and the name appears. Search finds it too.
Proper redaction removes the content. Think Pages redraws each redacted page as a picture with the black boxes painted in, so the hidden words no longer exist anywhere in the file. The rest of the page's text is put back as searchable text, so the document is still useful.
Key benefits
- Find it everywhereType a name and black it out on every page at once.
- One-tap detailsFind email addresses, phone numbers, account and card numbers, and postcodes with one tap each.
- Works on scansScanned pages and photos can be read with OCR so the search works on them too, or you can place boxes by hand.
- Nothing leaksRedacted pages can only be saved as a PDF or pictures, never as Word or text, so hidden words can't slip out another way.
How to redact a PDF
- Open Redact PDF and add the document.
- Type a name or number and press Black out to find every match, or use the buttons for emails, phone numbers, account numbers and postcodes.
- Drag across anything else on a computer, or tap Add box on a phone and drag the box into place. Check every page.
- Press Done, then Export PDF. Open the result and try selecting the blacked-out areas to confirm nothing is there.
Tips
- Search for each spelling and form of a name: "J. Smith", "Jane Smith", "Mrs Smith".
- Look for details outside the main text: headers, footers, signatures, photos and handwritten notes.
- Keep the original somewhere safe. Redaction can't be undone in the exported copy.
Questions
How can I check a redaction worked?
Open the exported PDF, try to select and copy the blacked-out area, and search for the hidden words. If nothing is selected and search finds nothing, the text is gone.
Does redaction make the file bigger?
A little. Redacted pages become pictures, which take more room than text. Pages without redactions are left as they are.
Does it catch everything automatically?
No tool does. It finds what you search for and common details, but always read through every page and add boxes for anything it missed.
Tools for this job
More guides
- Privacy and securityWhy use PDF tools that don't upload your filesMost online PDF tools upload your documents to their servers. Learn why browser-based PDF tools are safer for contracts, payslips, medical letters and ID, and how to check.
- Privacy and securityPassword-protect a PDF before you send itAdd a password to a PDF with AES-256 encryption before sending payslips, contracts or medical documents by email. Free, private and done in your browser.
- Privacy and securityBlack out details on a bank statement before you send itHide account numbers, sort codes and transactions on a bank statement before sending it to a landlord, lender or agency. The hidden details are removed for good, and nothing is uploaded.