Hello Adam,
I don't feel as though I'm the best candidate to provide an answer to your question. However I know that DNN at some point added a procedural functionality called Link Click that allows you to encrypt files and decrpyt them via an Encrypted ID. This feature enables you to keep the URL Path hidden from a user.
This is one of several threads in the DotNetNuke forums that discusses this feature:
http://www.dotnetnuke.com/Resources...posts.aspx I don't fully understand how to integrate Dynamic Forms to work with this built in functionality. However I've done something similar by saving GUID's as the file name. This way even if someone learns the location of the folder, they'll more than likely never be able to guess any file names that aren't accessible to them.
I openly state that this isn't my strongest suit, however if you conduct some research I'm certain that you'll find a viable solution.
Please let us know if you have any questions.
Thanks,
Ryan