Dropbox for iOS update adds a PDF viewer and file share notifications

Earlier today, Dropbox rolled out version 2.1 of its iOS app with a trio of enhancements in tow. The update, which requires iOS 5.0 or higher introduces a built-in PDF viewer, file sorting by date modified, and push notifications for when someone shares a folder with you (which were also recently added to the Android client). Whether you're a Dropbox power user or the casual type, this new software bump should definitely come in handy. If you're a stickler for keeping your apps current and you'v...