NullifyGuide · Security
How to redact a PDF permanently
Most people 'redact' a PDF by drawing a black rectangle over the text — and most of the time, the text is still there underneath. It can be selected, copied, extracted by a script, or exposed by simply deleting the shape. Permanent redaction means destroying the underlying content, and here's how to do it properly.
Why black rectangles fail
A PDF is a container of layered objects: text, images and shapes. Adding a black rectangle in a typical editor just adds another shape on top — the original text object remains fully intact in the file. Anyone can hit Ctrl+A / Ctrl+C on the page, open the file in an editor and delete the box, or run a one-line extraction script to read everything 'hidden' underneath.
There are well-documented real-world failures of this: court filings, government releases and corporate disclosures have all leaked names, account numbers and classified details because a box was drawn instead of a true redaction.
What permanent redaction actually does
Proper redaction removes the content from the file itself. Nullify does this by flattening each redacted page to an image and burning the black boxes into the page pixels — the underlying text object no longer exists in the exported file. There is nothing to select, copy or un-hide.
This also removes invisible risks like text layers behind scans, hidden OCR layers and metadata that a cosmetic box would leave behind on the redacted areas.
Step-by-step
Step 1
Open the Nullify editor and upload your PDF
Everything is processed in your browser — the file never touches a server. Scanned documents work too.
Step 2
Draw boxes over anything sensitive
Use the Draw Redaction tool. Move, resize or delete boxes until coverage is right. Or pay $2.99 to let AI find sensitive items across up to 50 combined pages.
Step 3
Review, then export
The export burns every accepted box into the page permanently and includes a PDF audit report of what was redacted.
Step 4
Verify the result
Open the exported file, try to select text in the redacted areas — there is nothing to select. That's the difference between covering and redacting.
Frequently asked questions
Can a permanently redacted PDF be reversed?+
No. Nullify replaces the page content with a flattened image where the redacted areas are destroyed. There is no hidden layer to recover — unlike black boxes drawn in standard PDF editors.
Does redacting a PDF remove metadata?+
Nullify rebuilds redacted pages as new page content, which removes the text objects in redacted regions. For full document hygiene also check the file name and any attachments before sharing.
Is there a free way to permanently redact a PDF?+
Yes — Nullify's manual redaction is free and unlimited, and runs entirely in your browser with nothing uploaded.
How is this different from Adobe Acrobat's redaction?+
Acrobat Pro's redaction tool is also a true redaction, but it requires a paid desktop licence and your workflow often routes files through cloud services. Nullify is free for manual use and keeps files on your device.
Redact your PDF now — free
Manual redaction is free and unlimited. AI-assisted detection is $2.99 for up to 50 pages combined across all your PDFs.
Start Redacting