Does redaction remove the text, or just cover it?
Replacing the text removes it from the file. Drawing a black rectangle over it does not — the text stays underneath and can be recovered. If the point is that the content is gone, replace it and save.
Can I redact text that appears in tables, notes and grouped shapes?
Yes, but you must walk them explicitly: text lives in shapes, table cells, grouped shapes and notes slides, and a pass over top-level shapes alone will miss the rest.
How do I make sure a redacted presentation cannot be reverted?
Save it as a new file and discard the original. Presentation formats retain revision and undo-related data, so editing in place is not the same as producing a clean copy.
Should I redact before or after converting to PDF?
Before. Redact the presentation, then convert — that way the removed text never reaches the PDF’s text layer, where it would otherwise remain selectable.
