DiskAid is free to copy files to and from the iOS device. It is faster and more reliable than iTunes to copy your PDF and other files to your device.
12-20-12 - Just tried to copy 3,844 files to my iPad 1 with iTunes 11. It just locked up and wouldn't do anything. Tried DiskAid and it worked fine. 3.8G of data.
WOW version 6.0 allows copying to unrealBook via WiFi. No more cables!!!!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.