> Properly hide text from others’ eyes
How can I redact personal information from a pdF so that no one can ever recover it?
Use a proper redaction feature in a reputable PDF editor. The problem is that the PDF format is archaic, dating back to the 1980s, and completely opaque. What you see on the screen in a PDF may bear little resemblance to the file’s contents.
Good editors like PDF Expert, PDFpenPro and Adobe’s high–end Adobe Acrobat Pro have a dedicated redaction feature, which should remove all redacted contents. Drawing black boxes over text and graphics is ineffective, as anyone can remove those boxes to reveal the content you don’t want them to see. This catches out lawyers and others every now and then, such as in Paul Manafort’s court case earlier this year (see bit.ly/wrdrdct).
Keep a locked copy of the original file, saved with a name that makes it clear that sensitive content is visible. Carefully follow the instructions for your PDF editor’s redaction tool; many will let you choose whether to replace redacted content with black boxes, as if redacted on paper using black marker pen, or just to blank out selected content with white.
Once you’ve finished, perform any additional clean–up offered in Acrobat, and save a “flattened” copy of the file. This rewrites the whole document from scratch, ensuring that the redacted content has gone and can’t be recovered (or, rather, uncovered). But there’s no easy way to check that, so you have to trust the app. If you can’t, print, use your black marker to redact, and scan back in.