Covering is not redacting
A black rectangle drawn on top of a PDF hides text only on screen. The words are still in the file: anyone can select them, copy them or pull them out with a text tool. Many leaked court files and reports were redacted exactly this way.
This tool removes the content for real. Every page that has at least one box is rendered as an image at the quality you choose, the boxes are painted into that image, and the image replaces the page. Text, pictures and drawings under the boxes no longer exist in the new file. Pages without boxes are copied unchanged, so their text stays selectable.
Find every occurrence at once
Type names, customer numbers or any phrase, one per line, and press Find and mark. All matches on all pages get a box. Ready patterns find email addresses, phone numbers, IBANs (checked with the IBAN checksum) and card numbers (checked with the Luhn algorithm), so random numbers are not marked by mistake.
Search works on the text layer of the PDF. Scanned pages are pictures and have no text to search: draw boxes on them by hand, or make the scan searchable with the OCR tool first.
What else is removed
The new PDF is built from scratch. Document information such as title and author, XMP metadata, bookmarks, attached files, comments and page thumbnails are not carried over. Links and form fields on pages without redactions are kept. Pages with redactions become images, so their text can no longer be selected or searched, and the file can get larger.