I’m also trying to figure out what possibilities for pdf annotation/editing there are in nextcloud but all I can find on this forum are lots of post with similar questions and cryptic solutions or open issues on Github.
Usually when I see this kind of silence on forums, it means either that the answer to the question is either too obvious for anybody to bother answering it or the forum is dying. Both don’t seem to be the case here, so I’m puzzled.