How to black out personal information in a PDF

Personal information can be found and blacked out in one pass with Protect, Find and mark in PDF by Zaweba. It searches the document for kinds of personal information by country, including emails, payment card numbers, IBANs, phone numbers, postcodes and National Insurance or Social Security numbers, and marks each for redaction. When you Apply the redactions, the text underneath is removed from the file. The app is free and works offline on Windows.

That's much safer than hunting by eye through a long bundle of letters, statements or case notes.

What it can find

Find and mark looks for words you type and for patterns by country. The general ones are emails, payment cards (checked with the Luhn test so random number strings aren't flagged), IBANs, dates, IP addresses and web addresses. For the UK it finds phone numbers, postcodes, National Insurance numbers and NHS numbers. For the US it finds phone numbers, Social Security numbers and ZIP+4 codes.

Names aren't a pattern, so add them as words to find. Type each person's name, and any other words that identify them, such as a house name or account reference.

Finding and marking the details

Open the PDF and choose Protect, then Find and mark. Pick the kinds of information you want and add any words. Run the search, and the app marks every match.

Go through the marks. Some matches may be fine to keep, such as your own organisation's phone number, so remove those marks. Some personal details may have been missed, perhaps a number written in an unusual way, so mark those by selecting the text or drawing over the area.

Choose the colour of the redaction boxes and any words to show over them, then Apply. The text and picture pixels under the marks are taken out of the file. Save as a new file and keep the original apart.

Pictures and scans

Apply removes picture pixels under area marks as well as text, so a photo, a signature or part of a scanned page can be blacked out by drawing a box over it. For a scanned page, search needs text, so the page may need text recognition before Find and mark can see the words. Until then, mark areas by hand.

Finishing the job

Blacking out the page is half of it. Then use Protect, Remove hidden information, which lists what the PDF carries with counts: document details, XMP, attached files, comments, form fields, invisible text, content off the page, bookmarks, scripts and links, and earlier versions. Remove anything that could carry personal data, or use Sanitise document to remove all of it.

Finally, test the saved copy. Search for a name or number you removed and try copying text where the boxes are. Nothing should come back.

Doing it regularly

If you redact the same kinds of document often, Tools, Actions can include a find and redact step alongside removing hidden information, and run on a folder of files. Check the results, because automatic finding is a help, not a guarantee.

PDF by Zaweba never uploads your files, so personal information isn't exposed to another service in the process of protecting it.