Why a black box does not hide text in a PDF
A common mistake: drawing a black rectangle over a name, phone number or account number and sending the PDF. The box hides the words on screen, but the text is usually still inside the file.
Try it yourself
Open a "blacked-out" PDF and:
- Press Ctrl+F and search for the hidden word, or
- Select the text under the box and copy it into a note
If the word is found or pasted, it was never removed. Anyone who receives the file can do the same.
Check a PDF before you send it
- Open Black-out check and drop the PDF.
- PatraPDF finds text hidden under black boxes, white-out and invisible text, and shows what it found and where.
- Choose Remove to delete those words for real. The page looks the same, but the text is gone from the file, and the file is checked again.
Redact from the start
To hide names, phone numbers, e-mails or ID numbers in a document, use Redact PDF. It finds them for you, deletes the text rather than covering it, removes hidden details such as the author's name, comments and attachments, and can give you a redaction log of what was removed, with the values masked.
Other places where hidden text survives
- Comments and sticky notes added by reviewers
- Earlier versions kept inside a PDF that was saved again
- Attached files inside the PDF
- The file's properties: author name, company, title
Run the Privacy scan to list all of these before sharing.
Questions
I used the black highlighter in my PDF app. Is that enough?
Usually not. A highlighter or drawn box covers the text but does not delete it. Run the Black-out check to be sure.
What about printing and scanning it?
A printed and scanned copy is only a picture, so the hidden text is gone, but the file becomes larger and cannot be searched. Proper redaction keeps the rest of the text searchable.
Is the check done on your server?
The check runs in your browser. Only the removal step uses the server, and the file is deleted right after.