Drawing a black rectangle over a word is not redaction. The characters stay in the file, and anyone who selects the page gets them back — which is how redacted filings keep ending up in the news.
Black out text →Free every day without an account on some tools. Your file is deleted the moment the job finishes.
The area is painted and then the page is flattened to an image, so there is nothing underneath to recover. The result is read back afterwards to check no selectable text survived anywhere, and you are told the answer. The cost is that the page is no longer selectable text; for a document being redacted, that is the point.
Yes. The words are removed from the file, not covered with a black rectangle that lifts off when the page is copied into another program.
Yes. On a scan the area is painted out of the picture itself.
Not from the redacted file, which is the whole point. Keep your original if you need it.