Definition - What does Redaction mean?
Techopedia explains Redaction
Redaction is often done on physical printed documents and not on the source files, so it becomes more like a post edit. An example is when a certain legal document needs to be distributed to people but not all of them have the right or privilege to view certain information contained in the document, and it must be kept intact for those who do. Rather than editing the source file, it is the printed copies that go to non-privileged individuals that get redacted, i.e., the information that the said individuals are not privy to is simply blacked out so as to become illegible.
This is a common practice within government agencies, especially those dealing with sensitive information and with certain legal documents that need to protect certain information but need to reveal other information in the same document. This is done to prevent tampering with the source material.