Security & Privacy
How to Redact a PDF Properly (Not Just Cover It Up)
Black boxes over text are not redaction — the words are still in the file. Here is how real redaction works and how to verify it worked.
Failed redaction has exposed witness names, unredacted settlement figures and classified passages in court filings, and it happens the same way every time: someone drew a black rectangle over the text and saved the file.
Why a black box is not redaction
A PDF page is a stack of drawing instructions. Adding a filled rectangle adds one more instruction on top. The text instruction underneath is untouched — it is simply covered, the way a sheet of paper over a screen covers what is displayed.
Select the area and copy it, and the clipboard contains the words. Extract the text and they are all there. Delete the rectangle and the page reads normally again.
What real redaction does
Proper redaction removes the underlying content rather than hiding it. The text instructions inside the marked area are deleted and the region is filled, so there is nothing left to recover — no copy-paste, no extraction, no undo.
How to redact
- 1Open the Redact PDF tool and add your document.
- 2Drag a box over each passage that must be removed, working from the page preview.
- 3Cover the whole passage — partial redaction leaves fragments that are often enough to reconstruct the rest.
- 4Apply the redaction and download the result.
- 5Verify: copy from the redacted areas and confirm nothing comes back.
What people forget to redact
- The same name appearing in a header or footer on every page.
- Document metadata — author, title and subject fields often name the person.
- Bookmarks and the outline, which can restate a redacted heading.
- File attachments embedded in the PDF.
- Comments and annotations left by reviewers.
- A filename that gives away exactly what you redacted inside.
Strip the metadata as a separate step. It is invisible in the reader and trivially readable by anyone who looks.
Redacting scans
A scanned page has no text objects to remove, so covering the area does destroy the information in the image. But if the document has been through OCR, there is an invisible text layer — and that layer still contains the words. Verify with copy-paste exactly as you would on a digital document.
Before you send it
- 1Copy from every redacted area and confirm nothing is returned.
- 2Search the document for the name or number you removed.
- 3Check the metadata.
- 4Check headers, footers and bookmarks.
- 5Have a second person look, if the stakes justify it.
Do it now
Redact PDF
Black out sensitive information. It runs in this browser tab — your file is not uploaded anywhere.
Open Redact PDFFrequently asked questions
Is drawing a black box enough?+
No. The text remains in the file and can be copied out. This is the single most common cause of accidental disclosure.
Can redaction be undone?+
Not when it is done properly — the content is deleted rather than hidden. Keep the original if you need it.
Does redaction remove metadata?+
Not automatically. Clear the metadata separately.
How do I redact a scanned document?+
The image area is genuinely destroyed by the redaction. If the file has an OCR text layer, check that too — the words may still be there.
How do I verify a redaction?+
Copy from the redacted area, and search the document for the removed term. Both should come back empty.