Workfront iPhone App and Request Forms

Is there a way to create a form field to allow upload from an iPhone's file folder section?

We've built a request form for our Sales team to ask for marketing collateral; however, because they're always on the road everyone wanted a way to submit via their company iPhones. The Workfront phone app (despite only getting I think 1½ out of 5 stars) actually works fairly well for just submitting requests; however, we've found one problem, if you put a field to allow someone to attach/upload a file from their computer, the app only directs them to the phone's photo storage area, nowhere else.

Is this a form setting or just a limitation of the system? And if it's a setting, does anyone know how to adjust for the file area of an iPhone?