The black box mistake
Drawing a black rectangle over text in a PDF editor looks like redaction, but the original text is usually still in the file underneath. Anyone can select it, copy it, or delete the rectangle. Several well-known leaks have happened exactly this way.
What real redaction does
True redaction removes the underlying content, not just hides it. The Play PDF redaction tool does this by flattening each page you redact into an image with the marked areas blacked out, so there's nothing left underneath to extract.
The trade-off is that a redacted page is no longer selectable text. Pages you don't redact keep their text.
How to do it
- Open the Redact PDF tool and add your file.
- Draw a box over each thing to remove. Drag a box to move it, or use its corner handle to resize it.
- Preview the result and check every box covers what it should.
- Download the redacted copy and keep your original separate.
Don't forget the other places data hides
Redaction handles what's visible on the page. A document can also carry its author name, title and keywords in its metadata. Clear those with the Edit metadata tool before you share it.