We are sorry about it. GoodNotes 3 has been discontinued and is only supported by iOS 7 or below because iOS 8 is not backward compatible with iOS 6 apps. The backup all process should still work to let you migrate all documents to the new GoodNotes 4 which is a paid upgrade and added many new features like iCloud sync, handwriting search, and iPhone support.
If GoodNotes crashes during startup, please reach out to us via email, so that we can help you recover your documents.