Relatedly (and this is probably not surprising to anyone here) if you draw a black box on a PDF file to cover sensitive information, chances are a simple screen reader will still able to extract the information just fine.
This way the redacted PDF won't have any metadata from the original (e.g. bookmarks) nor risk any weired PDF redaction bugs.
The downside is that your redacted PDF is (probably) larger than the original and isn't accessible. You can mitigate this by using OCR but it still isn't perfect and has a high chance of messing up tables or any special text placement.
Some fancy combination of encodings (e.g. using JBIG2 except for images) can probably help with the filesize.
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The best way to handle sensitive information is probably to use codenames (for people, places, etc) so you can share the original documents without worrying so much.
I think US courts and lawyers are finally starting to learn this.