Guide
How to redact a PDF on a Mac (and check that it worked)
Preview can genuinely redact a PDF. A black rectangle drawn with the markup tools cannot.
The difference is invisible on screen and obvious to anyone who selects the text. Whichever method you use, finish with the copy test below before you send the file.
Why a black rectangle isn't redaction
When you draw a filled shape over a name in a PDF viewer, you add an object on top of the page. The name stays in the file exactly as it was. Anyone can select the area and copy the text out, search the document for it, or open the file in another tool and see it plainly.
Governments and law firms have published documents this way and had the covered text recovered within minutes of release. It isn't an obscure trap. It's the default outcome of doing the obvious thing.
The copy test, first
Learn this before the methods, because it's the part that makes any method trustworthy. Do it on the finished file, every time.
- Open the file you're about to send.
- Press ⌘F and search for the name, the account number, or the last four digits you removed. There should be no match.
- Press ⌘A then ⌘C, and paste into TextEdit or Notes. Read what comes out. The removed text must not appear.
- If the page is a scan, zoom in hard on the redacted area. You're checking the pixels are gone rather than covered by something that might be moved.
Twenty seconds, and it converts a hope into a fact.
Method 1: Preview's Redact tool
Built into macOS, free, and the right default for a text PDF with a few things to remove. It's in Preview's Tools menu, listed as Redact, on recent versions of macOS. If you don't see it, update macOS.
- Duplicate the file first: File → Duplicate. Redaction is meant to be irreversible, so keep your original.
- Open the copy in Preview and choose Tools → Redact.
- Drag across each piece of text you want gone. It turns black as you go.
- Save. Preview applies the redactions to the saved file.
- Run the copy test above.
What to watch for. You have to find everything yourself, including the repeated header on page nine and the account number in the footer. Preview also won't touch the document's metadata, and on a scanned page the text is part of the image, so check that area visually rather than trusting a text search alone.
Method 2: Export the pages as images
A blunt fallback. Export each page as a PNG or JPEG, cover what you need to cover in the image, then combine the images into a new PDF. The original text layer is gone because there is no text layer any more.
The cost is real: the result isn't selectable or searchable, file size goes up, and anything you upload to an AI is now dependent on its own text recognition. Useful in a pinch, painful for anything long.
Method 3: Adobe Acrobat Pro
The paid standard. It has proper redaction plus a sanitise step that strips metadata, hidden layers, and attachments. If your work already pays for it, use it. A subscription is a lot to add for occasional personal documents.
Method 4: Cloaksmith
This is our app, so weigh it accordingly. The difference from the methods above is that it finds the personal details for you rather than asking you to spot every one: names, addresses, account numbers, dates of birth, and the rest. It removes the actual text and the underlying pixels, reads scanned pages with built-in text recognition, and gives you back a copy in the same format whose remaining text is still selectable. It handles several files or a whole folder in one pass.
It runs entirely on your Mac. Nothing is uploaded, there's no account, and it's a one-time $24.99 after 5 free documents. As with every tool on this page, including ours, no automatic detection catches everything, so review the result before you share it.
Don't forget the parts that aren't the page
- Metadata. In Preview, Tools → Show Inspector shows the author, title, and the software that made the file. These often carry a real name.
- The file name. Smith-payslip-March.pdf announces itself in the email before anyone opens it.
- Every page. Headers and footers repeat the things you most wanted gone.
- Word documents. Tracked changes, comments, and document properties survive a casual clean-up. Deal with those before converting to PDF.
- The message around it. Redacting the attachment and typing the account number in the email body is a common way to undo the whole exercise.
Which method to pick
- A few items, one text PDF: Preview's Redact tool, then the copy test.
- A scan, or many documents, or you're not sure what's in them: a tool that detects and removes for you.
- You already have Acrobat Pro: use its redact and sanitise together.
- One page, and you don't care about selectable text: export as an image.
Cloaksmith finds them so you don't have to
Drop in a PDF, Word file, or scan. Cloaksmith removes the personal details on your Mac and hands back a safe copy you can share with an accountant or an AI. First 5 documents free, then $24.99 once. macOS 15 or later on an Apple Silicon Mac.