Why a black box is not enough
Drawing a black rectangle over text in most PDF editors only hides it. The words are still in the file underneath, and anyone can select and copy them or remove the box. This tool rebuilds each redacted page as a picture with the boxes burned in, so the covered text, and every other piece of text on that page, is gone from the file you download.
Finding words to redact
Type a name, an account number, an email address or any phrase, and every match in the document is covered. Whole words stops a search for Ann from catching Annual, and Match case tells Smith apart from smith. Check every page before downloading: scanned pages have no text to search, so cover their details by drawing boxes.
Privacy
Redaction happens entirely in your browser. The PDF, your searches and the finished file never leave this device.