Checking a PDF for redactions that don't really hide anything

Badly redacted documents turn up all the time. Someone draws a black rectangle over a name, saves the PDF and sends it out, and the name can still be selected, copied and pasted. The check for unsafe redactions in PDF by Zaweba exists to catch exactly that before the document leaves your hands.

It looks for three kinds of problem, and for each one it offers to mark the spot so that Apply redactions removes the text for real.

What it looks for

The first is black or white boxes drawn over text that can still be copied. A black box is the classic mistake. A white box is sneakier, because the page looks as if nothing was ever there, yet the text sits underneath, ready to be found by a search.

The second is opaque comment boxes over text. A filled rectangle added as a comment looks just like a redaction on screen, but comments are separate objects on top of the page. They can be moved or hidden, and the text beneath them is untouched.

The third is redaction marks never applied. Marking is only the first half of redaction. Until Apply is used, the marks are proposals and the text is still in the file. It's easy to mark everything carefully, save and forget the last step.

Fixing what it finds

For each problem, the check offers to mark it for redaction. Accept, and the area is turned into a proper redaction mark. Then use Apply redactions, and the text and picture pixels under the marks are removed from the file. The cover-up becomes a real removal.

Look over each finding before you accept it. A dark box over text is sometimes a deliberate design, such as white text on a dark heading band. The check can't know your intent, so read each one and decide.

When to run it

Run it before sending any document that has had information hidden, whoever did the hiding. It is especially useful for documents you've inherited. If a colleague prepared a file and says it's been redacted, the check tells you in moments whether that is true.

It's also a good final step on your own redactions. Even if you used proper redaction marks, running the check confirms none were left unapplied.

The rest of the clean-up

Unsafe redactions are about what's on the page. A document can also leak through what isn't visible. After fixing redactions, run Protect, then 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 actions, links and earlier versions) and lets you tick what to remove. Earlier versions deserve a special mention, because an earlier save of the document may still hold the unredacted text. Sanitise document removes all of those at once.

A quick test you can do yourself

After applying redactions and saving, open the saved file and try to select text where a redaction sits. Then search the document for a word you removed. If neither finds anything, the text is gone. That simple test, together with the check, gives you real confidence.

Because PDF by Zaweba does all of this offline, you can check sensitive documents without sending them to a website first, which would rather defeat the purpose.