I needed to split a 53MB (yes, large) PDF document in two. There are so many "PDF Splitters" out there that just, well, don't work. How annoying to spend time with those.
This one worked for me:
AnyBizSoft PDF Splitter and you can download it via CNET here: http://download.cnet.com/AnybizSoft-PDF-Splitter/3000-18483_4-75211444.html
Hope that saves you some frustration.
I hesitated to add what didn't work, but thought it would be helpful. This one just didn't work for me:
PDF Splitter - Spent too much time and in the end never got it to work.