How to redact sensitive data in a PDF for real (no fake black box)

How to redact sensitive data in a PDF for real

To truly hide sensitive data in a PDF you have to erase the content, not just cover it. In AtlasDocs you drag a bar over the passage, the tool turns that page into an image with an opaque black rectangle burned on top, and you check the result before downloading. Whatever sat under the bar no longer exists in the file: it can't be selected, copied or recovered.

1. Open the Redact sensitive data tool and upload your PDF (it works on one file at a time). Every page is shown at full size on screen.
2. Drag with the mouse, or your finger, over each passage that must disappear: ID number, name, signature, photo. Mark as many areas as you like, on as many pages as you need. Each bar has an ✕ to remove it, and the "Clear 3 bars" link (the number follows what you marked) wipes them all so you can start over.
3. Click "Redact and review" (with areas marked, the button shows the count, such as "Redact 3 areas and review"). The tool processes the file and opens the "Review before downloading" step, showing the document already redacted.
4. Check that the bars cover everything that should vanish. Missed something? Click "Back to edit". All good? Click "Download redacted document": the file is saved with the suffix -tarjado.pdf.

Unlike scribbling a black box in a regular viewer, here the marked area isn't laid "on top" of anything: the whole page is redrawn as an image, and the pixels under the bar come out black. When you download, you get a file in which the information simply no longer exists at that spot.

Why a black box on top hides nothing

A PDF stores text and images in layers. When you draw a black rectangle over a number or a name in a PDF reader, you're only adding one more layer, and the original data is still there, intact, underneath. Selecting the text and pasting it elsewhere, or opening the file in a program that shows the layers, is enough to make the content reappear. That's how "redacted" official documents have leaked: the box was only a visual decoration.

What the tool does (and what it doesn't)

• Only the pages that received a bar become images; the others are copied as they were, with their text intact.
• On a redacted page the text is no longer selectable or searchable, because the page became a photo of itself. If you still need that page's text, extract it before redacting.
• The bar is an opaque black rectangle, with a small margin around it, burned into the page's pixels. There is no transparency and no "undo" after the download.
• The action is irreversible, and the tool says so on screen. Keep the original somewhere else if you will need it.
• There is no search by word: you mark each occurrence by hand. In long documents, locate the passages first with your PDF reader's search, then redact them one by one.
• One PDF at a time; the downloaded file gets the suffix -tarjado in its name.

Common things to redact

• ID, passport and account numbers in contracts, receipts and powers of attorney.
• Home address, phone number and email on forms, records and résumés.
• A handwritten signature that shouldn't float around in copies sent to third parties.
• Amounts, salaries or clauses you need to omit before sharing a contract as a template.
• Photos and stamps in scanned documents, which the bar covers just like text.

Redaction and data protection

Data protection rules treat personal data as something that must be safeguarded by whoever handles it. If you send a document where a sensitive detail is only covered by a fake box, that detail is still exposed, and the responsibility for a leak is still yours. Erasing the information before sharing is the correct way to reduce that risk.

Redaction handles what is visible on the page. But a PDF also stores data that never shows on screen: the author's name, the program that created the file, creation and edit dates, an internal title. Before sharing, run the redacted document through the Clean hidden data tool, which strips those fields with one click and lists what was removed.

Everything happens in your browser: the PDF is processed on your own device and is never sent to any server. The data you want to protect never leaves your computer, which matters even more when the whole point is sensitive information.

Take your time in the review step: it exists because redaction can't be undone. Zoom into the preview and check the edges of every rectangle before clicking "Download redacted document".