Some encouraging features are present in Adobe Cloud - Just would like to find out further whether they support annotation changes only and a quick sync. Wouldn't mind paying for that sort of service I guess.
Just out of interest - Found this between adobe and dropbox
https://blogs.dropbox.com/dropbox/20...e-partnership/
Between Xodo and dropbox in particular
"Dropbox changes are saved as you go, and Google Drive files are re-synced when you close the file"
Found here
https://blog.xodo.com/2015/04/09/9-r...do-pdf-reader/
Useful to know since one of the features I am after is minimizing data usage by just being able to sync annotations (and differential annotations only)
Some cross platform apps for reference:
https://pdf.wondershare.com/pdf-edit...nnotation.html