How to redact a PDF properly, and why black boxes are not enough

Before sending a contract, a court filing, a medical report or an internal document outside your company, you often need to hide names, ID numbers, addresses, amounts or bank details. Data protection laws make sharing personal data that the recipient does not need a legal risk, not just carelessness. And the most common way to "redact" a PDF does not work.

The black box mistake

Drawing a black rectangle over the text, whether in a PDF editor or in Word before exporting, only changes how the page looks. The original text is still inside the file, under the box. Anyone can select and copy it, find it with the PDF reader's search or extract it with ordinary software. Official documents and court records have leaked in exactly this way, with redactions that came undone with a simple copy and paste.

What proper redaction means

Proper redaction means the information no longer exists in the file. Covering the text is not enough: it must be gone. The safest way to guarantee that is to rebuild the page with the redacted areas already painted in, so that the final file only contains the image of the page, with no text underneath.

How to do it with the Redact PDF tool

In Redact PDF you mark what to hide in two ways:

• By hand: drag the mouse over the page to draw a box. It works for anything, including signatures, photos and stamps.
• By search: type names, contract numbers or other phrases, and the tool marks every occurrence in the document. Search ignores accents and case. You can also mark email addresses and long numbers, such as IDs, account and card numbers, automatically, with or without punctuation.

When you download, every page with a box is redrawn as an image with the black areas already applied, and its original text leaves the file. Pages without boxes stay exactly as they were, with selectable text. Everything happens in your browser, and the document is never sent to a server.

How to check the redaction worked

1. Open the redacted PDF and try to select the text under a box. Nothing should be selected.
2. Use the PDF reader's search (Ctrl+F) with the hidden name or number. The search should find nothing.
3. Go through every page: the same piece of data often appears more than once, in headers, footers or attachments.

Extra precautions

Always keep the unredacted original in a safe place, because redaction cannot be undone. Remember that the same data can be written in different ways, such as an ID with and without separators or an abbreviated name. In scanned documents, which are already images, automatic search cannot find the text: mark those areas by hand.

Frequently asked questions