2] Convert the file If the above fix does not work, you can convert the file to the latest version of OneNote. Before proceeding, copy the notebook and paste it to another location to create a backup.

Microsoft's OneNote app for Windows 10 will now allow the editing of attached files. The new ability is currently being rolled out to Office Insiders, and will come to more channels later.

OneNote 2016 will magically sync it to the cloud along with the rest of your notebook contents. Best of all, the same trick also applies to Office documents and regular text files.