I don't own an iPad but I'd assume it's the same as adding stuff to an iPhone.
Open iTunes and go to 'books' on the navigation pane on the left. Drag and drop the QRH PDF for the MD11 into the main window. Then plug in your iPad and go to 'DEVICES' and go to the 'books' tab there and make sure sync books is ticked. That's off the top of my head anyway, I'm pretty sure that's correct. Other then that you could just email yourself a copy of the QRH and make sure you have iBooks installed on your device.
Oliver P
If I remember correctly, I think this has something to do with switching model/livery from 'in game. I think to fix this, you can get away with loading a default FSX plane and then reloading the pmdg 737 you desire.
This has always worked for me in the past anyway.
Oliver P