Is your phone jailbroken?
It better be, if not, then you wont be able to do that.
If you got iTunes 9, then use DiskAid (freeware), just google for it. But if you still (like me) have >iTunes9 i.e. 8, then use something like iTunes Tunnel Suite.
Basically using those applications you can browse your iDevices file system, which Apple doesnt want you to. This allows you to backup and modify files.
Using something like DiskAid, just SSH into your phone (i.e. connect your phone to your computer using DiskAid) and browse to that directory "var/mobile/Applications/xxxx/documents". There you will be able to save it.
Hope this helps.
(Sorry, I'm in a rush)