How to Redact a PDF

Step-by-step: four ways to redact a PDF

Pick the section that matches what you already have installed. Two of these four methods cannot truly redact — those sections say so up front and give you the workaround rather than pretending otherwise.

Verify it worked — a 30-second test

Regardless of which tool you use, run this two-step verification on every redacted PDF before you share it:

1. Copy-paste test. Open the PDF in any reader. Click-and-drag across the redacted area as if you were selecting normal text. Then press Ctrl+C (or Cmd+C) and paste into a text editor. If anything appears, the redaction is fake — the underlying text survived.
2. Text-extraction test. Open a terminal and run pdftotext yourfile.pdf - (the pdftotext tool ships with most Linux distributions and is free for macOS via Homebrew or Windows via the Xpdf project). The output is every text fragment in the file. Search it for any term you intended to redact. If you find it, the redaction is fake.

The text-extraction test is more reliable than the copy-paste test because PDF readers sometimes refuse to select over an overlay even when the underlying text is there. pdftotext doesn't render — it just walks the content stream and reports every string it finds. It bypasses any visual trickery.

If either test surfaces the redacted content, your tool did an overlay rather than a removal. Redo the redaction with a tool that does content-stream removal.

Why most "redaction" removes nothing

Every failure above has the same cause: a PDF stores what is drawn on the page separately from the text content of the page. A black rectangle is simply a new drawing instruction added on top. It hides the pixels. It never touches the characters, so any reader — or search engine, or screen reader, or plain copy-paste — can walk straight past it and read the original.

This is not a rare edge case. We pulled 72 published "redacted" PDFs and checked them: 17% still leaked recoverable text, including 31% of the US federal ones. That study has the full breakdown of who leaked what and how. The rest of this page explains the mechanism, so you can avoid joining the list.

How PDFs actually store text

A PDF page is described by a content stream — a sequence of drawing instructions. To render the word Hello at coordinates (100, 200), the content stream contains something like:

The string (Hello) is the actual text. It's in the file as plain characters (often compressed, but trivially recoverable). When a PDF viewer renders the page, it executes the content stream and the word appears. When you copy-paste from the rendered view, the viewer pulls the same string out of the content stream.

Now suppose someone draws a black rectangle over the word in their editor. The editor appends a new instruction to the content stream:

The rectangle is drawn after the text, so it visually covers it. But the (Hello) Tj instruction is unchanged. The text is still in the file. Any reader that walks the content stream sees both — and most ignore the rectangle when extracting text.

Overlay redaction vs. content-stream removal

There are two materially different operations both called "redaction" in casual use:

1. Overlay redaction. Add a black shape on top of the original content. The original survives in the file. This is what Word, Google Docs, macOS Preview, most online "redaction" tools, and some PDF editors do — even when their UI calls it "redact".
2. Content-stream removal. Parse the content stream, identify the text and image operators that fall inside the redacted area, and delete those operators from the stream. Then write the modified PDF. The redacted content no longer exists in the output file.

Only the second is genuine redaction. The output of the first is functionally a screenshot with embedded plaintext underneath.

The difference also matters for image content. Overlay redaction over a face or signature leaves the original pixels in the file — anyone who decompresses the image stream gets the unredacted picture back. True redaction either removes the image object entirely or replaces it with a blacked-out version compressed back into the same stream slot.

Which tools do which

The table below covers the tools people most often reach for. "Overlay" means the original content survives in the file. "Stream" means the content is removed.

The cleanest combinations from a privacy standpoint are Essex Redact (stream removal, files stay on your device, free) and Foxit PhantomPDF (stream removal, local, paid). Adobe Acrobat Pro can do real redaction but the workflow has a footgun — marking is not applying, and many users save after marking, producing a PDF with unredacted content under draft overlay marks.

Why "browser-only" matters for redaction specifically

For most file operations, "the file is uploaded to a server and processed there" is fine. Compressing an image, converting a format, generating a thumbnail — none of those carry sensitive content the recipient shouldn't see. Redaction is the opposite. The entire point is that some specific bytes shouldn't be visible to anyone except your intended audience. Sending the file to a third party to remove those bytes is a contradiction: the bytes you're trying to hide are now sitting on someone else's server.

Online redaction services solve this with promises — "we don't keep your files", "we encrypt in transit", "the file is deleted after 1 hour". Those promises are unverifiable from your side. You uploaded the file. Whether it was deleted afterwards is a policy claim, not a fact about your data.

Browser-only redaction is verifiable. The redaction code runs in the same browser tab you're sitting in. The file never crosses the network. You can prove this with a simple test: open the redaction tool, then disconnect from Wi-Fi, then redact and download. If the tool keeps working, no upload happened — there's no other explanation. Our redaction tool passes this test. Try it below.

Try true redaction yourself

The redaction tool on this site runs entirely on your computer. It does true content-stream editing — not an overlay. The actual redaction code runs in your tab, talks to no server, and writes the output file directly into your downloads folder.

FAQ

How do I redact a PDF for free?

Use a browser-based tool that removes content instead of covering it — the redact tool on this site is free, with no signup, no upload and no page caps. The free tiers of most online redaction services will also do the job, but they upload your document to their servers first, which defeats the point for anything genuinely confidential.

How do I redact a PDF on a Mac?

Not with Preview alone — its black rectangles leave the text in the file. Either use a browser tool that deletes the content, or follow the Preview flatten workaround above and verify the result. Acrobat Pro on macOS does redact properly, provided you click Apply.

Can I redact a PDF on my phone?

A browser-based redaction tool works on a phone, because the work happens in the browser itself. Marking small regions accurately on a phone screen is fiddly, though — where a missed field would matter, do it on a computer with the whole page in view.

Is redaction reversible?

Real redaction is not. The content is deleted from the file and there is nothing left to recover, which is exactly why Acrobat warns you before applying — so always keep an unredacted original elsewhere. Fake redaction, of course, is trivially reversible. That is the whole problem.

Why does my "redacted" PDF still show the original text when I copy and paste?

Because the tool you used drew a black rectangle on top of the text instead of removing it. The original characters are still in the PDF's content stream — any modern PDF reader can select and copy them. This is the most common redaction failure across word processors, online tools, and even some paid desktop apps.

Is redaction in Microsoft Word safe?

No. Highlighting text in black or covering it with a black shape in Word, then exporting to PDF, produces a PDF where the original text remains selectable. Word does not have a true redaction feature. The same applies to Google Docs and LibreOffice.

Does Adobe Acrobat redact properly?

Adobe Acrobat Pro has a true Redact tool that removes content from the underlying stream — but only if you click Apply, not just Mark. Many users save the file after marking but before applying, which produces an unredacted PDF. The Acrobat Standard tier and the free Reader do not include this feature.

Is online redaction safe for confidential documents?

Most online redaction tools upload your file to a server, redact there, and send you a download. The file leaves your device. For legal, medical, or financial documents the right rule is simple: if the redaction tool requires an upload, do not use it for sensitive material. Browser-only tools that run the redaction on your computer avoid the upload entirely.

How can I verify my PDF is actually redacted?

Open the PDF in any reader. Move your cursor over the redacted area and try to select text with click-and-drag. If nothing highlights and copy-paste produces nothing, the content is genuinely gone. For a stronger test, run pdftotext yourfile.pdf - in a terminal and search the output for any term you intended to redact.

Does redacting a PDF also strip metadata?

Not automatically. PDF metadata — author, title, creation tool, edit history — lives outside the content stream. A real redaction removes the marked text and images but the document properties can still leak information. After redacting, also clear the PDF metadata: Acrobat exposes this under Document Properties, and most PDF libraries can wipe it programmatically.

Can I redact images and signatures, not just text?

Yes. Our redact tool removes image objects that fall inside the marked area, not just text. The output PDF doesn't contain the original image bytes at all — they're stripped from the file along with the text characters.