What comes back is a picture of your document. That is the point — rebuilding each page as an image is what destroys the covered text. It also means the file will no longer be searchable or selectable, and it will be several times larger. Keep your original.
Drop a PDF or a photo here
or tap to choose · nothing is uploaded
Marking
page 1 of 1
Drag across anything you want gone. Tap a mark to take it off again.
How it works: drawing a black rectangle in Word, Preview or most PDF editors only paints over the words — anyone can select the text underneath and copy it straight out. Lawyers and government departments have leaked names this way. Here each page is redrawn as a fresh image with your marks burnt in, then a new file is built from those images, so the covered characters no longer exist anywhere in it. The whole thing runs in this tab: your file is never uploaded, and the copy you download is the only one that leaves.