I will apologise if this is already on here but have had a quick look and couldn't find it.......
When i tried to create a book using youblisher i had multiple pdf copies of the student's work. The problem with youblisher is that i needed them as one complete file.
So, found this website http://foxyutils.com/mergepdf/
It lets you combine multiple pdf files into one, and it's free which makes using Youblisher alot easier :-)