I've added a line to the abilities table to clarify that adding/removing related documents and attachments are at same permissions as editing the document.

All roles except Reviewers should be able to Link Related Documents.

This is currently the case.

All roles should be able to upload documents.

I think you mean "All roles should be able to add attachments", is that right? If so, I disagree. That would mean in a public document that someone (anyone) could register and then upload files and make them visible to everyone who views that document. I think on our call we came to the conclusion that being able to add attachments to issues would be enough for reviewers.

Closing because I believe reviewers being able to attach files to issues is suitable.