Why a black box is not redaction
A PDF is built in layers. A black rectangle, a highlight or a "comment" box is drawn on top of the page; the text underneath is untouched. Anyone who receives the file can:
- select the area and copy the text into Notepad,
- search the document for a name or number and jump straight to it,
- delete or move the rectangle in any PDF editor.
The same goes for covering text in Word and then saving as PDF. This mistake has exposed court filings and government documents many times. Real redaction removes the content and puts a black box where it used to be.
How to redact a PDF in MadPDF
- Download MadPDF (free, no account) and open your PDF.
- Open the Protect & redact tools and choose redaction.
- Mark what must go: select text, draw boxes over images or areas, or search for a word or number and mark every match (useful for a name, an ID number or an account number that appears many times).
- Review the marks, then apply the redaction. This is the step that actually deletes the content.
- Save as a new file (for example
contract-redacted.pdf) and keep the original separately.
Arabic and mixed English/Arabic documents work the same way: search for the Arabic word and it is marked and removed like any other text.
Remove the hidden information too
Redacting the visible page is only half the job. A PDF can also carry:
- Metadata: author name, company, software, original file name and dates in the document properties.
- Comments and form data left by reviewers.
- Attachments, bookmarks and hidden layers that can repeat the information you just removed.
Use MadPDF's option to remove hidden information before saving the redacted copy. If the file goes outside the company, you can also password-protect it or restrict copying and printing from the same Protect tools.
Check the redaction worked
- Close and reopen the saved redacted file.
- Search (Ctrl + F) for a word you removed. There should be no match.
- Select across a black area, copy, and paste into Notepad. Nothing readable should appear.
- Open the document properties and check that the author and title don't give anything away.
It takes a minute and is worth doing every time before you send the file.
Scanned pages and images
On a scanned page the text is part of a picture, so search won't find it. Draw the redaction box over the area of the image instead. If the scan has an OCR text layer (from running OCR), redact it too, otherwise the hidden OCR text still contains the words. Photos of ID cards, signatures and stamps should be covered with area redactions in the same way.
Why not redact online?
To redact a document online you first have to upload the complete, unredacted version, with every name, ID and number you are trying to protect, to someone else's server. For HR files, contracts, medical and legal documents that defeats the purpose. MadPDF opens, redacts and saves the PDF on your own PC; it goes online only to check for updates, to reach a timestamp or certificate server when you sign, or when you choose to send feedback.
FAQ
Does a black highlight or box redact a PDF?
No, it only covers the text. See why a black box is not redaction.
Can redaction be undone?
Not in the saved redacted file; the content is gone. Keep the original and save the redacted copy as a new file.
How do I know the redaction worked?
Search for a removed word and copy from a black area into Notepad. Nothing should come back. See the checks.
Can I protect the PDF after redacting?
Yes: add a password or restrict printing and copying. To sign it as well, see how to sign a PDF offline.