Apple IAP Downloadable content

Couple of questions: did not see these answered anywhere already.

I have  content that I would like to move to an IAP scenario.  Audio and books actually.  I have considered simply hosting the files and when the user selects the productID and payment confirmation happens I call a network download which then allows the menu item to be “clickable” with the link already present in the lua file.  I have noticed that Apple allows for the storage of files for you.  So the real question is how do I link to those files?  Are they downloaded to the system.documents dir and I simply reference them as the filename when they are downloaded via apples backend?

Anyone have a full working version of IAP for iOS working in a fashion like this?

Thanks,

Matt