Notebooks 8 and Notebooks 10 provide a convenient method for migrating your documents directly on the device, without duplicating it. A detailed guide is available on this site.

However, you can also set up Notebooks 10 without migrating documents from Notebooks 8, and instead import the documents from your Dropbox or a WebDAV server by setting up the same sync method that you have been using in Notebooks 8.

How to Get Documents from Notebooks 8 to Notebooks 10