DropCopy is one of the best programs available from the App Store that lets you transfer files between iOS devices. DropCopy – easily share files and clipboard text between iPhones, iPod Touches and Macintosh computers.

How it works
When 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 select the file you want to copy, and the destination; DropCopy takes care of the rest. To get files from the Mac to your iPhone, simply drag a file onto our discreet “dropzone” on your desktop and it is transferred immediately to your chosen destination.

DropCopy has file previews for most common media types, including Word, PDF, and many others.