You need to backup everything except the Inbox folder. If you need to restore the files, do not copy the Inbox folder back to the iPad.
Here is a step by step PDF that you can read on how to do a manual backup AND how to copy to a new iPad
Here's a video showing how to get to the iTunes file sharing window for Windows computers. In this case, substitute unrealBook instead of Azul:
Here is a PDF that describes how to backup your unrealBook files with iTunes 12
How to backup with iTunes 12
Here is another link - just substitute unrealBook for FamViewer
Connect your iPad to the computer.
In the left sidebar of DiskAid, select Storage->Apps->unrealBook
Drag files into the files listing to the right of the unrealBook icon.