Guides › Redact a PDF

How to redact a PDF properly

If you hide an ID number or account number in a PDF and the text can still be copied, the redaction has failed. Covering text and removing text are two different things.

Why a black box isn't enough

Many people redact by drawing a black rectangle over the text. It looks hidden, but the text is still inside the PDF. Anyone can select across the box and copy it, search for it, or remove the rectangle in an editor and read the original. Leaks caused by exactly this mistake have been reported many times.

How PdfMonster's redact tool works

The Redact tool removes the text that overlaps the area you mark from the PDF's content, and then draws a black box in its place. To use it:

Pick Redact in the toolbar (shortcut X).
Drag over the text you want to hide. You can mark several areas.
Press Download. The redaction is applied at that moment, and a message such as “removed N text object(s) from the PDF” appears.

Things to know

Overlapping words are removed whole. PDFs often store text as word- or line-sized pieces, so a piece that your box touches even slightly is deleted entirely. Text outside your box may disappear with it — check the result.
Text inside images isn't removed. In scans and screenshots the text is pixels, not text. You'll get a warning if an image lies under the box; the box only covers it. For such files, fix the source document instead.
Redactions are applied when you download. If you rotate or delete a page first, the redactions so far are merged into the PDF before the page operation runs.

How to check that it worked

Open the downloaded PDF in any PDF viewer (your browser, Acrobat, and so on).
Drag across the black box, or press Ctrl+A to select everything, copy it, and paste it into a text editor.
Search (Ctrl+F) for the words you redacted. There should be no matches.
You can also reopen the file in PdfMonster and confirm that the line is empty.

Important: always run these checks before sending a document that contained personal information. PdfMonster doesn't upload your file, so your original never leaves your computer while you work.

Try the redact tool