Well, all you can basically do is scribble within a PDF. The RM2 doesn't offer proper PDFs annotations and it doesn't even come close to the Supernote in terms of other useful features like bookmarking, digests, etc.
> EDIT: Wow. Looked at the A5X and for the price compared to the RM2, it's very enticing.
Yup, exactly. It seems more expensive upon first sight but it's actually a pretty good deal.
> Do you know if there's any API that allows me to write my own utilities to sync with the A5X? Specifically, I want to be able to send PDFs to the device programmatically that will be eventually synced the next time I use it.
This is exactly what I'm waiting for, too! My hope is that once they open up their platform I'll be able to install the Syncthing Android app and sync my Supernote with all my other devices over WiFi.