Cubasis 3 Multitasking on iPad?

Cubasis 3 on iPad: I want to use the sound for a midi-piano in the cubasis 3 app and at the same time I want to read an pdf-file with songtext (mulitasking).
If I use the multitask-function on the ipad, it works, first i start cubasis, then i open the pdf-app over multitasking. My problem is: I want to hear the sound and want to see the pdf in full size. Has anybody experience with this kind of task? Thanks!

If you select Background Audio under “Setup”, you can let Cubasis run completely in the background and, for example, use the pdf reader in full screen mode.