How to Redact in Preview on Mac (Spoiler: You Can't)

If you're on a Mac and need to redact a PDF, Preview is the obvious first place to look. It opens PDFs natively, it has markup tools, it can draw shapes and highlight text. Surely it can redact a document?

It can't. Preview has no redaction feature. Every tool it offers — rectangles, highlights, markup — creates an annotation that sits on top of the text. The text underneath is completely intact and trivially recoverable.

This isn't a limitation that Apple is likely to fix. Preview is a viewer with basic annotation tools, not a document security application. But because it's the default PDF app on every Mac, thousands of people use it to "redact" documents every day — and every one of those documents is leaking the information they thought they hid.

What People Try (And Why It Fails)

Drawing a Black Rectangle

The most common approach:

The result looks perfect — a solid black box covering the text. But it's just a shape annotation layered on top of the PDF's text layer. The original text is untouched. Anyone who receives this file can:

• Open it in any PDF editor and delete or move the rectangle to reveal the text
• Select All (Cmd+A) and copy the entire page — the text under the black box copies along with everything else
• Use Cmd+F to search for words they suspect are under the redaction
• Run pdftotext in Terminal — it ignores annotations entirely and outputs all text in the document

Using the Highlight Tool

Some people try using the highlight tool with a dark color to obscure text. This is even less effective than a rectangle — highlights are semi-transparent by design, so the text is often still partially visible. And like rectangles, the highlight is an annotation that can be removed in any PDF editor.

Drawing Over Text With the Pen Tool

Using Preview's freehand drawing tool to scribble over text in black ink is another annotation. It can be selected and deleted just like shapes and highlights. The underlying text remains.

Cropping the Page

Preview's crop tool (Tools → Rectangular Selection, then Tools → Crop) is sometimes used to cut off parts of a page that contain sensitive information. This is slightly better than annotations because it changes the visible area of the page.

However, Preview's crop doesn't actually delete content outside the crop area. It sets a crop box that tells PDF viewers which part of the page to display, but the full page content — including everything outside the crop — remains in the file. Some PDF tools can reset the crop box and reveal the hidden content. It's not safe for redaction.

A Quick Test You Can Do Right Now

If you've ever "redacted" a PDF in Preview, here's how to check whether it actually worked:

1. Open the "redacted" PDF in Preview
2. Press Cmd+A to Select All text on the page
3. Press Cmd+C to copy
4. Open TextEdit or Notes and press Cmd+V to paste

If the text you covered with a black rectangle appears in the pasted output, your redaction did nothing. The text was there the whole time.

For a more thorough test, open Terminal and run:

pdftotext /path/to/your/file.pdf -

This extracts every piece of text from the PDF, completely ignoring any annotations. If your "redacted" text shows up, the file is not safe to share.

What to Use Instead

Since Preview can't redact, Mac users need a different tool. There are two options that actually work:

Option 1: Adobe Acrobat Pro ($23/month)

Acrobat Pro has a dedicated Redact tool (Tools → Redact) that marks areas for redaction and then permanently removes the underlying text when you click "Apply Redactions." It's the industry standard, but it requires a paid subscription and you need to remember the two-step process — marking is not the same as applying.

Option 2: Flatten to Image (Free)

The foolproof method is to flatten redacted pages to images. This converts each page into a flat image (like a high-resolution PNG) so that no text layer, no annotations, and no hidden data exist in the output file. There's nothing underneath the black boxes because there's no "underneath" — it's just pixels.

This is what Safely Redact does. You open your PDF in the browser, draw redaction boxes over the sensitive areas, and export. Every page is rendered as a flat image at 150 or 300 DPI. The original text is physically destroyed during the rendering process.

It works on any Mac (or any computer) because it runs entirely in the browser — no app to install, no subscription, and your file never leaves your device. For Mac users who just need Preview but with actual redaction, this is the closest thing.

Summary

• Preview has no redaction feature. Rectangles, highlights, pen marks, and crops are all non-destructive — the text survives.
• Test with Cmd+A, Cmd+C, Cmd+V. If the text pastes, it's not redacted.
• The safe alternative is to flatten pages to images so no text data exists in the output file.
• Never share a "redacted" PDF from Preview if the document contains anything sensitive — Social Security numbers, financial data, medical records, legal information, or personal details.

Related

• Why Drawing Black Boxes on a PDF Doesn't Actually Redact Anything
• How to Redact in Word (And Why It Doesn't Actually Work)
• Remove Metadata From a PDF