Redact a PDF — Permanently Remove Sensitive Content

A black box is a shape drawn on top. The text remains in the content stream underneath, so selecting the area and copying it reveals everything — this is the mistake behind a long series of published documents leaking exactly what they meant to hide. Here the page is re-rendered as an image with the area painted out before the image is made, so the characters no longer exist in the file.

Because that is the only way to guarantee removal in a browser. Surgically deleting individual glyphs from a content stream while leaving the rest intact needs a full PDF writer and still risks missing a copy in a form field or an annotation. Rasterising is blunt, but it is provably complete — and it is applied only to the pages you actually marked.

Not from the file. Someone could run OCR on the visible remainder, exactly as they could with a printed and rescanned page — but the redacted area is solid black pixels, so there is nothing there to read.

Usually yes. The document information dictionary records the author name from the operating system account and the application that produced it, which frequently identifies the person or department you were trying not to name. It is on by default.