I have had trouble using the SongBook alternative for using iTunes for simple file movement between my Laptop and iPAD. I found free iFUN software on iTunes very useful. You simply connect via the standard Apple charging / lightning cable bring up iFUN on the laptop and choose SongBook+ and choose the create sandbox option. All the Songbook files appear and you can freely copy them to and from the iPAD SongBook+ path.
Thank you for the tipp. I assume the full name of this iTunes alternative is iFunBox? (http://www.i-funbox.com/en/index.html)