Can a Redacted PDF Be Unredacted?

The Short Answer

Often, yes. Drawing a black box or a black highlight over text in a PDF only covers it. The words are still in the file, and anyone can select them, copy them and paste them somewhere else.

Real redaction deletes the text, so there is nothing left to uncover. You can test any PDF in about ten seconds, and fix one in your browser.

The 10-Second Test

1. Open the redacted PDF in any PDF viewer.
2. Click on the page and press Ctrl+A (Windows) or Cmd+A (Mac) to select all, then Ctrl+C or Cmd+C to copy.
3. Paste into a plain text editor, such as Notepad, or an empty email.
4. Look for the words you blacked out. If they are there, the PDF is not redacted.
5. Also search the PDF (Ctrl+F or Cmd+F) for one of the hidden words. A match under a black box means the text is still there.

For a long document, the PDF Text Extractor pulls out every word on every page. The Redact PDF tool's Check a PDF for hidden text mode goes a step further and points out text that sits under a dark box. It works by looking at the rendered page, so treat it as a helper, not a guarantee.

We tried it on a test PDF with a Social Security number covered by a solid black rectangle. The number looked hidden, but the check listed it under the box and the full text contained it.

Why a Black Box Isn't Redaction

A PDF page is a stack of drawing instructions: put this text here, this picture there. When you draw a black rectangle, add a black highlight, or place a comment box, you add one more layer on top. The text underneath is untouched. Viewers show the box, but copy, search and text extraction read the text.

Covering-only redaction has caused public embarrassments. In January 2019, a court filing by Paul Manafort's lawyers had black bars over passages that could be revealed by copying the text and pasting it into a new document, as the Columbia Journalism Review reported.

Real redaction removes the content itself. Dedicated redaction tools edit the page so the text is gone. The Redact PDF tool takes the blunt route: every page with a box becomes a flat image with the box burned in, so no text survives on that page.

How to Redact a PDF Properly

1. Open the Redact PDF tool and choose your file. It stays on your device.
2. Drag a box over every name, number, signature or picture that has to go. Check each page, including headers and footers.
3. Click Redact & download. Boxed pages become images; other pages are kept as they are.
4. Run the 10-second test above on the downloaded file before you send it.

The trade-off: redacted pages lose their selectable text, and the file usually gets bigger. The PDF Compressor can shrink it again.

Things That Trip People Up

• Highlighting in Word, then saving as PDF. A black highlight is formatting on the words, so the words go into the PDF with it.
• Marks that were never applied. Tools with real redaction often work in two steps: mark the areas, then apply. Marked but unapplied areas still contain the text.
• Covering a scanned page. If the page is a photo or scan, a box drawn in a PDF editor is a layer over the picture. The full picture can still be in the file.
• Metadata and bookmarks. The document's title, author, keywords, bookmarks and comments live outside the page and can repeat a name you blacked out. Apple notes that in Preview, table-of-contents entries that link to redacted text aren't removed.
• The same detail elsewhere. A name redacted on page 1 may appear again on page 7, in a running header, or in the file name.
• Box size gives hints. A box's width shows roughly how long the hidden word was. For short names, cover a little extra.

Mac, Adobe Acrobat and Windows

Mac (Preview): Preview has a real redaction tool. Show the Markup toolbar and use Redaction Selection to select the text. Apple's guide says you can change the redaction while you edit, but once you close the document it becomes permanent. Don't use the Shapes tool to draw a black rectangle instead: that is markup on top of the page. Source: Apple, Annotate a PDF in Preview on Mac.

Adobe Acrobat: redaction is a paid feature. Adobe's plan comparison lists “Redact sensitive information” for Acrobat Pro and Acrobat Studio but not Acrobat Standard, and the free Acrobat Reader is for viewing. Adobe's redaction tutorial has you mark content, then select Apply, then remove hidden information. Until you apply them, marks are only marks.

Windows, Chromebook or no paid software: the Redact PDF tool runs in any modern browser and does not upload your file.

This guide explains how PDF files work. It is not legal advice; if a court, employer or regulator sets rules for how documents must be redacted, follow those.