GoodNotes documents can get quite large over time. Synchronizing (and backing up) them on constantly uses ridicules amounts of data (sometimes up to 1GB in a single day).
Using GoodNotes in school, this poses a big problem, as we currently don't have working WiFi. Connecting my iPad to my iPhone's Personal Hotspot is always a story of force closing GoodNotes, connecting to the Hotspot, doing whatever, disconnecting and relaunching GoodNotes as I have a limited amount of high speed cellular data.

To solve this, GoodNotes could support iOS native Low Data Mode, which users can set system wide on a per network basis. To support this, GoodNotes should pause automatic sync and automatic backups when low data mode is set. This would allow to pause automatic sync/backup on the metered cellular data and then resume the operations on the non-metered home WiFi. For users that don't want this behavior, there could be a toggles in settings for sync and auto backups to be disabled separately from each other for when you want to see changes on other devices but backups can wait.