One thing that the iPhone is currently missing is a quick way to transfer files between other iOS devices. DropCopy is one of the better programs available from the App Store that solves this problem.
If you load up the app on two separate iOS devices connected to the same Wi-Fi network, such as an iPhone and iPad, both devices will see each other. You can then select the file you want to copy and the destination you want to copy it to and the app takes care of the rest. There's also a limited file viewer built-in that works with a range of formats including Word and PDF files. If you want to try out the app before purchasing, there's a free Lite version that supports the file sharing features, but does not include the previewing support and doesn't allow you access to your photo library
DropCopy is a great little tool for quick and easy transfers between iOS devices.