1. Search or select
Search for words such as a name or account number, or draw boxes over areas.
2. Apply and check
Apply the redactions, then try to select or search the removed text in the result.
3. Clear hidden details
Use Edit PDF metadata to strip the title, author and other properties stored in the file.
Good to know
Drawing a black box in an editor does not remove the text underneath. Redaction removes it, so check by searching the saved file for the hidden words.
Questions
How do I know redaction worked?
Search the saved PDF for a word you redacted. It should not be found.
Related: Edit or remove PDF metadata