Redaction
Redaction is the permanent removal of protected text from a document before it is disclosed or filed.
The failure mode is famous: a black rectangle drawn over text that is still selectable underneath. A redaction that can be undone by copy and paste is not a redaction.
Anything that removes text has to remove it from the file itself, not from the way the file is displayed.
Related: Privilege review, Anonymisation
Legalnaut builds this out of your own case file. See the plans.