How to redact sensitive information in a PDF

Redaction failures make headlines: someone draws a black box over text, but the text is still underneath and can be copied out. True redaction removes the content, not just the view of it.

The classic mistake

Drawing a black rectangle in a viewer only covers the text. Select-all and copy, and the "hidden" words come right out. Never rely on a shape to redact.

Real redaction

Proper redaction deletes the underlying text and flattens the page so nothing remains beneath the mark.

Do not forget metadata

Names and history often hide in document metadata. Strip it as part of any redaction pass.