How to redact a PDF on a Mac (properly)

With PDF Unlimited (free)

1. Make a copy

   Redaction is permanent, so work on a copy. Duplicate the file in the Finder first.

2. Switch to Redact mode

   Open the copy in PDF Unlimited and click Redact in the toolbar mode switcher.

3. Mark what to remove

   Drag a box over each name, number, signature or image you want removed. Use ⌘F to find every mention of a name or account number so you do not miss one.

4. Apply Redactions

   Click Apply Redactions. The content beneath each box is deleted from the file.

5. Save and verify

   Save, then search the file with ⌘F for a redacted word. It should not be found.

With Preview, built into macOS

1. Duplicate first

   Preview saves automatically, so choose File > Duplicate and work on the copy.

2. Choose Redact Selection

   Show the Markup toolbar and choose the Redact Selection tool, then select the text you want to remove.

3. Close to make it permanent

   Redactions can be adjusted while the document is open. They become permanent when you close it.

Why a black rectangle is not redaction

Drawing a black shape over text hides it on screen. The text is still in the file, underneath. Anyone can select it, copy it, search for it, or delete the rectangle. Over the years, plenty of court filings and official reports have leaked exactly this way.

True redaction removes the content itself, then marks where it was. After you apply it, there is nothing left under the box to recover.

What about Preview?

Preview has a Redact Selection tool in the Markup toolbar, and Apple says it removes the selected text and becomes permanent once you close the document. It works on text you can select. Apple also notes that table-of-contents entries pointing to redacted text are not removed, so check the outline as well.

PDF Unlimited lets you drag a box over any area, including images and signatures, and shows an explicit Apply Redactions step so you know exactly when content is removed.

A redaction checklist

Before you send a redacted file:

• Search with ⌘F for each redacted name or number. Nothing should come up.
• Check headers, footers and page margins. Names hide there.
• Look at the Outline in the left sidebar for bookmarks that give things away.
• Check images, stamps and signatures, not just text.
• Remember the file name. Redacting a document called Smith-Divorce-Settlement.pdf is only half the job.

Scans need extra care

A scanned page is an image, so drag the redaction box over the picture of the words. If the scan has been made searchable with OCR, there is also a hidden text layer. Apply Redactions removes the content under the box, but run the ⌘F check anyway to be sure nothing outside a box mentions the same detail.

Questions