DeepRedact / How to redact a PDF on Mac

How to redact a PDF on a Mac

Your Mac can redact PDFs properly, for free, with no extra software. But there are two tools in Preview that look almost identical, and only one of them actually deletes anything. This is the method that works, the trap that catches people, and how to check your own work afterwards.

The short version

Open the PDF in Preview. Choose Tools → Redact (macOS Ventura or later). Drag across the text you want gone. Then — and this is the part people skip — use File → Export as PDF rather than a plain Save. Exporting flattens the document and writes out a file with the redacted content genuinely removed.

If you used a black rectangle from the Markup toolbar instead, stop. That is not redaction, and the text underneath is still in the file for anyone who receives it.

Redacting in Preview, step by step

1. Work on a copy. Redaction is destructive by design. Duplicate the file first so you keep an unredacted original for your own records.
2. Open it in Preview and go to Tools → Redact. Your cursor becomes a redaction tool.
3. Drag across each piece of text you need removed. A black bar appears as you go.
4. Check every page. Preview redacts only what you mark — there is no search, and no automatic detection. A social security number on page 40 of a deposition will survive unless you find it yourself.
5. Choose File → Export as PDF. Not Save, not Duplicate. Export is what forces Preview to write a flattened file with the marked content actually gone.
6. Close without saving if prompted about the original, so you do not overwrite your reference copy.

The Markup trap that leaks documents

Preview has a second toolbar — Markup — with a rectangle shape you can fill black. It looks exactly like a redaction once applied. It is not one. The rectangle is an annotation drawn over the page; the characters underneath remain in the PDF's text layer, fully intact.

Anyone who opens that file can select the area, copy it, and paste out the text you thought you had removed. No special tools, no forensics — just Cmd-C. This is the single most common cause of accidental disclosure in documents that were, in the sender's mind, redacted.

The distinction matters because the two tools sit one menu apart and produce visually identical results. The only way to tell them apart afterwards is to try to copy the text.

How to verify it actually worked

Never assume. Check, every time, with whichever of these fits:

• Select and copy. Open the exported file, drag-select across the black bar, press Cmd-C, and paste into TextEdit. Nothing should come out.
• Search the document. Press Cmd-F in Preview and search for a string you removed — a name, the last four digits of an account number. Zero results is what you want.
• Read it as plain text. In Terminal, run mdls -name kMDItemTextContent yourfile.pdf, or open the file in TextEdit, and look for anything that should be gone.

That last check catches something the first two miss: text that survives in metadata, annotations or an embedded thumbnail rather than the visible page. Those are the four places redacted content tends to hide.

Scanned documents

If the PDF came from a scanner or a phone camera, the page is an image and there is no text layer to remove. Preview's Redact tool will still draw over it, and in that specific case the underlying pixels are replaced, so the result is genuinely gone.

The risk with scans is different: because there is no searchable text, you cannot use Cmd-F to find what needs redacting. Every page has to be read by eye. On a 200-page scanned client file, that is where mistakes happen — not from a technical failure, but from human fatigue.

Where Preview stops being enough

For one file with a handful of items, Preview is genuinely the right answer and you should use it. It stops working when:

• There are many files. Preview has no batch mode. Fifty documents means fifty manual passes.
• The documents are scanned. Nothing is searchable, so nothing can be found automatically.
• You need to prove it. Preview produces no record of what was removed. If a supervisor, a court or a regulator asks what you redacted and how you know it held, you have nothing but your word.
• The same items recur. One client's name across a whole case folder means finding it manually in every single file.

Related

• Best redaction software in 2026 — including the free options, compared honestly.
• Adobe Acrobat alternatives for Mac — what actually replaces it, job by job.