iCloud lets you store your GoodNotes documents in online iCloud servers and keep them up to date across your devices. Documents are synced efficiently because each time you make a change, only the difference are transferred but not the entire file. If you have another iOS device, just log-in to the same iCloud account and enable iCloud in GoodNotes (Options > Settings > iCloud) and then your documents will be downloaded from iCloud automatically.
What is iCloud?
