How to redact a PDF properly, and why a black box isn't enough
Published · 2 min read
Time and again, court filings and government reports have made the news because the “redacted” parts could simply be copied out. The black boxes were real, but the text underneath them was still in the file. Here's how to avoid that mistake.
Why covering text doesn't remove it
A PDF page is built in layers. When you draw a black rectangle or a highlight over a sentence in most editors, you add a new layer on top. The sentence is still stored underneath as text, so anyone can select it, copy it, search for it or delete the rectangle.
The same goes for white boxes used to “erase” something, for changing the text colour to black, and for annotations. They change what the page looks like, not what the file contains.
What real redaction does
Proper redaction removes the content itself. In Redact PDF, each page that has a redaction is rebuilt as an image with the boxes burned in. The hidden text, its fonts and anything else beneath the boxes are no longer in the file, so there is nothing left to copy or uncover.
Pages without redactions are left unchanged, so the rest of the document keeps its selectable text.
Redact a PDF step by step
- Open Redact PDF and choose your file. It is processed in your browser and never uploaded, which matters for exactly the kind of document you're redacting.
- Search for names, account numbers or other words to mark every occurrence at once, and draw boxes over anything else, such as signatures or photos.
- Review every mark, then export a new copy. Your original file is not changed.
Check these before you share
- Scanned pages: search only finds text the PDF stores as text. A scan is a picture of text, so draw boxes over it by hand, or run OCR first to make it searchable.
- Redacted pages become images: their text is no longer selectable, and links and form fields on those pages are removed. That's the price of real removal.
- Metadata and bookmarks aren't redacted: a name can still sit in the document's author field or in a bookmark title. Use Sanitize PDF to remove metadata, attachments and scripts as well.
- Test the result: open the exported file, try to select and copy text where the boxes are, and search for one of the redacted words. Nothing should come back.