An error occurred while saving the commentAnon commented
I've just fond another app that has all the features for annotating PDFs that OneDrive used to, and so many more: PDF viewer - Annotation Expert.
It is identical to the original OneDrive tools (and free!), but you can also open multiple files in tabs, change the scrolling view, etc.
It works with the iPad Files app and syncs to OneDrive almost instantly, so there is no need to make copies of documents.
This sounds like I'm just promoting the app, but it genuinely fixes all the disappointment from recent OneDrive updates.