How to Redact a PDF So the Hidden Text Is Really Gone

To redact a PDF, you have to remove the text, not just cover it. A black box drawn in most PDF editors sits on top of the page, and the account number underneath can still be copied. Use a redaction tool that turns the redacted pages into images, then check the result by trying to select the hidden text.

Updated 5 Oct 2026By Sandesh Karwa

Why a black box doesn’t hide anything

A PDF page is built in layers. The text is stored as real characters, and anything you draw with a highlighter, shape or comment tool is added as another layer on top. On screen the number looks covered. In the file it is still there.

Anyone who gets the file can recover it in seconds:

select the covered area and copy it, then paste into a note;
open the PDF in another app and delete or move the box;
search the PDF for the number, which finds it under the box.

This has caught out lawyers and governments, not only ordinary users. A study of US court records confirmed nearly 200 filings where text under black rectangles could be read, and the US National Security Agency published guidance in 2006 warning against exactly this. Highlighting text in black, or using a black font colour, has the same problem.

When you need to redact

Redact whenever you share a document but the receiver needs only part of it:

Bank statements sent to a landlord, visa office or employer: hide other transactions, the full account number and balances they don’t need.
Salary slips and Form 16: hide PAN, bank account and employee ID where they aren’t asked for.
ID copies: hide the parts of a PAN, licence or passport page that aren’t relevant.
Medical reports and contracts: hide names, phone numbers and addresses of other people.

For Aadhaar, there is a better first step. UIDAI lets you download a masked Aadhaar from myaadhaar.uidai.gov.in. It replaces the first eight digits with xxxx-xxxx so only the last four show, and it is a valid proof of identity. Our driver onboarding guide walks through downloading it and removing its password.

How to redact a PDF, step by step

Open the PDF in Redact PDF. If it is password-protected, remove the password with Unlock PDF first.
Draw a box over each thing you want to hide: an account number, a name, a whole row of transactions. Draw boxes on every page where the item appears. A number in the header often repeats on each page.
Save the redacted PDF. Each page with a box is turned into an image with the black boxes burned in, so the text underneath no longer exists in the file. The file’s metadata (author, title, the app that made it) is removed too.
Check it. Open the new file, press Ctrl+A (or Cmd+A) on a redacted page and copy, then paste into a note. Search for the hidden number with Ctrl+F. Neither should find it.
Send the new file, not the original. Keep the original yourself.

What changes in the redacted file

Redacted pages become pictures. Their text can’t be selected or searched, and links and form fields on those pages are gone. Pages without boxes are not touched.
The file may get bigger, because an image of a page usually weighs more than its text. If a portal has a size limit, run the result through Compress PDF.
Digital signatures stop being valid, because the document has changed. A handwritten signature in a scan stays visible.

Mistakes that leak information anyway

Missing a repeat. Account numbers appear in headers, footers and summary boxes. Search the original for the number first so you know every page it is on.
Box too small. Leave a margin around the text. A sliver of the top or bottom of digits can be enough to guess them.
Leaving the total. If you hide some transactions but leave the running balance, the hidden amounts can be worked out.
Hiding the wrong thing on a scan. On a scanned page, the number is already part of the picture, so a box drawn by most editors can still be removed. The flattening step fixes this too.

Questions

Does drawing a black rectangle in a PDF redact the text?

Usually not. Most PDF editors and annotation tools add the rectangle as a layer on top of the page. The text underneath is still in the file, and anyone can select it, copy it or delete the rectangle. Proper redaction removes the text itself.

Does printing to PDF or taking a screenshot remove the hidden text?

A screenshot does, because it is only a picture of the page, but it loses quality and you have to do every page by hand. Printing to PDF is not reliable: depending on the app, the text under the box can be carried into the new file.

Should I redact my Aadhaar number myself?

For Aadhaar, first download a masked Aadhaar from UIDAI. It replaces the first eight digits with xxxx-xxxx and shows only the last four. Redact it yourself only when you have a photocopy or scan and no masked copy, and when the receiver doesn’t need the full number.

Why can’t I select text on the redacted pages any more?

Because the redacted pages are turned into images, which is what removes the hidden text. Pages you didn’t redact keep their text. If you need searchable text again, run the result through an OCR tool such as Image to text, which reads only what is visible.