Real redaction · Not a box on top
Redact a PDF properly: black out text without leaving it underneath
Blacking out a PDF looks easy: open an editor, draw a black rectangle over the name, save. The catch is that the text is usually still there. Select it, copy it into another document, or search for it with Ctrl+F, and whatever you thought was hidden comes straight back. Black highlighting and movable annotations have exactly the same weakness.
In Spain, plans are arranged with our sales team.
Anonimatum performs real redaction: the marked text is removed from the file and an empty black box takes its place. Before that, Anonimatum's own AI models, running on EU servers, find names, ID numbers, addresses, phone numbers and IBANs, and show you a preview of every match so you decide what goes and what stays. Signatures, stamps and QR codes that are not text can be covered with visual zones in the same pass.
When the result is generated, the file metadata is stripped too, and scanned PDFs go through OCR before detection so image-only pages do not slip through. The document you send contains exactly what you see on screen, and nothing else, so you can share it by email or upload it to a portal without a second thought.
How to black out a PDF in Anonimatum
- 1
Upload the PDF
Open it at app.anonimatum.com in your browser, with nothing to install. If it is a scan, OCR first recognizes the text on image pages.
- 2
Check what will be blacked out
AI and patterns flag the personal data. In the preview you untick what must stay visible and draw a zone over anything that is not text, such as a signature.
- 3
Apply redaction
The marked text is deleted from the PDF and replaced by an empty black box with nothing underneath.
- 4
Test it and download
Try to select or search for the blacked-out text: there is nothing to copy. Download the PDF and send it with confidence.
Fictitious document
Before and after: a formal demand letter
Fictitious letter from a tenant to a landlady asking for the deposit back. Names, ID number, home address, bank account and phone are blacked out.
Sender: Andrés Molina Ruiz, ID no. 12345678Z
Address: C/ Olmo 14, 3.º B, 41003 Sevilla
Addressee: Carmen Vidal Ortega
Re: return of the deposit under the lease dated 1 March 2024
I request repayment of €1,200 within 15 days
by bank transfer to ES00 0000 0000 0000 0000 0000.
Contact phone: 600 000 000
Sender: (redacted), ID no. (redacted)
Address: (redacted)
Addressee: (redacted)
Re: return of the deposit under the lease dated 1 March 2024
I request repayment of €1,200 within 15 days
by bank transfer to (redacted).
Contact phone: (redacted)
The subject, amount and deadline stay because they are the substance of the demand; everything that identifies the parties is removed from the PDF, not merely covered.
Why a black rectangle is not enough
The text is still in the file
A rectangle or black highlight is just another layer. Underneath, the characters remain and can be selected, copied or indexed.
Search gives it away
Search a badly blacked-out PDF for the ID number and the viewer finds it. With real redaction the search returns nothing, because the text no longer exists.
Metadata talks too
File properties can hold names or details you never see on the page. Anonimatum strips the metadata when it generates the redacted document.
Review before, not after
Real redaction cannot be undone, so the preview shows you every match before you apply it rather than after the file has gone out.
Blacking out PDFs: frequently asked questions
How can I tell if a PDF has been blacked out properly?
Run two tests: select the blacked-out area and paste it into a plain text editor, then search with Ctrl+F for a word that should have disappeared. If anything shows up, the text is still underneath. In a PDF redacted with Anonimatum neither test returns the data.
Does printing and rescanning the PDF work?
It removes the text layer, but it is slow, degrades quality and does nothing about what you missed: anyone who runs OCR on the copy gets back everything you did not black out. Detecting, reviewing and redacting the original is more reliable.
Can I black out signatures, stamps or photos?
Yes. Visual redaction lets you place zones over handwritten signatures, photos, stamps or QR codes and redact them in the same pass as the text.
Can a blackout be undone?
No. Redaction is irreversible because the text is deleted from the file. If you will need the original data later, use pseudonymization with an equivalence map instead of blacking it out.
Where is my PDF processed?
On servers in the European Union, by Anonimatum's own AI models. The document is not sent to external language model APIs and is deleted after processing.
Black out your PDF with real redaction
Upload a document at app.anonimatum.com, review the detections and download a PDF where the blacked-out text no longer exists.
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