To redact a PDF properly, the text has to be removed — not covered. A black box drawn in Edge, a black highlight, or a shape added in Word sits on top of the words, and anyone can still copy, search or extract them. Use a real redaction tool that deletes what's underneath, then check the saved copy: press Ctrl + A, copy, and paste into Notepad. If the hidden words appear, the redaction failed.
This guide explains why the common methods fail, the free ways that do work, and how to check any redacted PDF before it leaves your hands.
Why Black Boxes Don't Redact a PDF
A PDF page is built in layers. The text you read is real text, with each letter stored at a position on the page. When you draw a black rectangle in a PDF viewer, or add a black highlight, you add a new layer on top. The words underneath are untouched. They are still:
- Selectable — drag across the box, copy, and paste anywhere
- Searchable — Ctrl + F finds them, even though you can't see them
- Readable by software — any PDF text extractor, screen reader or AI tool reads them as normal
- Removable — in many editors the box itself can simply be deleted
Methods That Don't Work
- Drawing a box or highlighting in Microsoft Edge — adds a mark on top; the text stays.
- Black highlight or a shape in Word, then "Save as PDF" — the words are still in the file under the shape.
- Changing the text colour to black or white — the text is still there; select it and it reappears.
- "Print to PDF" after drawing boxes — the printed PDF usually keeps the text layer, so the words are still under the box.
- Cropping a page — the cropped area is often still in the file and comes back when the crop is removed.
Methods That Do Work
1. Delete the text at the source, then make a new PDF
If you have the original Word document, delete the confidential words themselves (or replace them with [REDACTED]), then save a new PDF. Nothing to hide means nothing to leak. Before you do, remove the document's hidden data too — see how to remove metadata from Word documents — because tracked changes and comments can still contain the deleted text.
2. Use a true redaction tool
A real redaction tool removes the text under each box and then saves a new file. Adobe Acrobat Pro does this with its Redact tool (a paid subscription; the free Acrobat Reader cannot redact). On Windows, Redact PDF does it offline: it finds personal data for you, removes it for real, and checks the copy afterwards.
3. Turn the page into a picture (last resort)
Exporting each page as an image after covering the text, then rebuilding the PDF from the images, also works — but the document is no longer searchable, file sizes grow, and it's slow for more than a few pages.
Redact PDF finds names, addresses, account numbers, National Insurance, passport and HKID numbers, phone numbers and emails, lets you tick each box, then saves a new copy with that information permanently removed — and reads the copy again to check none of it can be found. Scanned pages included. Everything runs on your PC; nothing is uploaded.
Try it free — Microsoft StoreHow to Check a Redacted PDF Before You Send It
Do this with every redacted PDF you receive or send — it takes under a minute:
- Open the redacted copy in Edge or any PDF reader.
- Press Ctrl + F and search for a word you redacted (a surname, an account number). It must not be found.
- Press Ctrl + A, then Ctrl + C, and paste into Notepad. Read what comes out around each box.
- Try to click and drag a black box. If it moves or can be deleted, it's a drawing, not a redaction.
- Check the file's properties (right-click → Properties → Details): the author and title can name people too.
What About Scanned PDFs?
A scanned page is a picture, so there's no text to copy — but that doesn't make a box on top safe. The box is still a separate layer that can be removed, and many scanners add an invisible text layer (OCR) so the page can be searched, which carries the words underneath. A proper redaction tool changes the picture itself and removes any hidden text layer.
Don't Forget the Hidden Parts of the File
Even with every visible word redacted, a PDF can still give information away through:
- Document properties — author, title, subject, the software and computer it came from
- Bookmarks and the outline — chapter titles that include names
- Comments and annotations — reviewers' notes, often with their names
- Attachments — files embedded inside the PDF
- Earlier versions — PDFs saved with "incremental updates" can contain the page as it was before the change
Redact PDF builds the redacted copy from scratch, so properties, attachments, bookmarks and scripts from the original are not carried over.
Who Needs to Redact PDFs?
- Subject access requests (SARs) — under UK GDPR, information about other people usually has to be removed before you send someone their data
- Solicitors and barristers — disclosure bundles, exhibits and court filings
- Accountants and finance teams — statements, payslips and invoices shared with third parties
- HR — investigation reports, references and grievance files
- Everyone — bank statements for a tenancy application, documents for a dispute, anything posted online
Frequently Asked Questions
Is a black highlight enough to redact a PDF?
No. A highlight or a drawn box only covers the text. The words are still in the file and can be copied, searched or extracted. Use a redaction tool that removes the text, then check the copy by searching for a redacted word.
Can Microsoft Edge redact a PDF?
No. Edge can draw and highlight on a PDF, but it doesn't remove the text underneath, so it isn't safe for redaction.
Can a redacted PDF be un-redacted?
If it was redacted properly — the text removed and the file saved fresh — no: the information isn't in the file any more. If boxes were simply drawn on top, yes: the text can be copied out or the boxes deleted.
Is there a free way to redact a PDF properly?
Yes. Delete the text in the original document and save a new PDF, or use a redaction tool. Redact PDF is free to try on the Microsoft Store and works offline. The free Adobe Acrobat Reader can't redact; Acrobat Pro can.
Do I need to redact third-party data in a subject access request?
Usually, yes. The ICO's guidance is that you generally shouldn't disclose other people's personal data when responding to a SAR unless they consent or it's reasonable to do so without consent. Redacting their names and details is the common way to do that.
Does Redact PDF upload my documents?
No. Detection, redaction and the check after saving all happen on your PC. There's no account and no cloud.
Redact PDFs the right way
Redact PDF finds personal data, removes it for real and checks the copy — offline, no account.
Learn more →Related guides: How to remove metadata from Word documents · Don't send a contract with hidden metadata · How to remove GPS location from photos
About Beginza — Beginza builds privacy tools for Windows that run entirely on your device. No cloud, no accounts. Browse all apps at beginza.co.uk.
Percy Ng
Co-founder of Beginza. Builds privacy tools for Windows that run 100% locally — no cloud, no accounts. All Beginza apps are available on the Microsoft Store.