FileMagnet is an app that allows you to transfer files to your iOS devices. There are two parts of this app, one is the app that you install on your iPhone, iPod or iPad, and the other one is the "uploader" or desktop app. This installs both on Windows and Mac OS X and allows you to send files to the iOS device. The desktop app is absolutely free, but you need to the iOS app for it to be of any use, and it is $4.99 at the App Store.
When you have the FileMagnet app running on both your iOS device and your Mac, they will connect automatically. If for any reason they fail to connect automatically, you can use the manual connection dialog to input your iOS device's IP address. Once a connection has been established, you can simply drag and drop files to the window and they will be sent to the device. You can also drag files before a connection is made and they will be uploaded at the moment, when connection is available.
The iOS app allows you to open most popular file formats. You can open text files in a variety of formats, including PDF and DOC. It also supports video and audio files. There is also security available in the form of a password lock down.