You can import documents through iTunes File Sharing by dragging documents into the GoodNotes 5 folder in iTunes. Please make sure that your iPad is connected via USB to your computer when you use iTunes File Sharing. For an explanation of iTunes File Sharing, please review this guide by Apple.
The next time you open GoodNotes 5 when you dragged and dropped documents to the iTunes File Sharing Folder, GoodNotes will ask you automatically if you want to import the files.
When should I use iTunes File Sharing?
Most cloud storages are powerful enough to handle large data but for very large documents the cloud storage you're using may not be able to handle the file size which will cause a failed import or a crash. In this case, we recommend using iTunes File Sharing.