Hey Cameron -
Thanks for entering the GHOP contest and for choosing to contribute to the Joomla! community. I want to point out a resource that might help you with process questions. When you have a moment, please read GHOP Contestants Please Read: Task Process Start to Finish
Now, as to your question, couple things to check:
1. One limitation on uploads is that spaces not be included in the filename. Double check to see if that is your problem.
2. Also, *.pdf must be listed as a allowable extension in your Global Configuration/system tab. So, please check that, as well. It is the Media Settings, section, legal extensions (file types) option. The default list is:
Please - let us know of any questions you have. We are here to help you be successful with your task. Thanks!