How to redact a PDF properly
Updated November 4, 2026 · 6 min read
Redaction means permanently removing sensitive information, such as names, account numbers, addresses or medical details, before a document is shared. Done wrong, it is one of the most common ways confidential data leaks.
The mistake: covering instead of removing
Drawing a black rectangle over text in most PDF editors, or highlighting it in black, only adds a shape on top. The original text is still in the file. Anyone can select it and copy it out, search for it, or delete the rectangle. Court filings and government reports have exposed supposedly hidden details this way more than once.
True redaction removes the underlying content so it no longer exists in the file.
How to redact a PDF with PDFHeron
- Open the PDF in the Redact PDF tool. It runs in your browser, so the document is never uploaded.
- Choose Redact and drag a box over every piece of sensitive information. Redaction areas are outlined so you can review them.
- Save the PDF. Every page with a redaction is flattened into a high-resolution image with the boxes burned in, so the covered text is gone from the file.
The trade-off: flattened pages are images, so their text is no longer selectable. Pages without redactions are unaffected.
Don’t forget the hidden places
- Metadata. The document title, author and subject can contain names or project codes. Check and clean them with Edit PDF metadata.
- Headers, footers and file names. A file called “Smith-divorce-settlement.pdf” undoes careful redaction inside it.
- Repeated information. Search the document for every occurrence of a name or number, not just the first one.
- Images. Signatures, ID photos and screenshots may contain sensitive text too. Redaction boxes work on images as well.
How to check your redactions
- Open the saved file in a different PDF reader.
- Try to select and copy text in the redacted areas. Nothing should come out.
- Use the reader’s search for a redacted word. It should not be found.
Redact vs. whiteout vs. delete
- Redact: permanent removal, shown as a black (or colored) box. Use for anything sensitive.
- Whiteout: visual cover only. Fine for fixing typos on scans, never for secrets.
- Delete text: removes text objects from the page while keeping the rest of the page as real text. Good for cleaning up, but use Redact when you need a visible, verifiable black-out.