You might expect to be able to open a Goodnotes backup file outside the app in order to view your Goodnotes documents.
However, that .zip file is only meant to be re-imported to Goodnotes to restore your library. You can also unzip the file and import any of the .goodnotes files within into Goodnotes for further editing.
If you'd like to be able to view your backed-up notes, you can do either of this:
- Let the app back up notes automatically in PDF format, and check the auto-backup cloud storage.
- Export the entire library in PDF format.