In order for FM GO to access a file, it must be in the FM GO "sand box". It cannot find/open files located outside that area--such as a file in a drop box account.
Found something interesting on this - and the original request/question above DID NOT include the fact that all the work was being done off of the iPad. we use the iPad only for viewing purposes. Tried to do everything on iPad this time and it worked flawlessly
It can actually work
1. Upload file to dropbox shared folder
2. copy link to shared file to clipboard
3. paste on FM text field
4. That same field is the CUSTOM URL/Web address for the FM web Viewer
5. Once PDF link is generated on web viewer, click on the download button and PDF gets rendered within the web viewer