If you're someone with files spread across multiple cloud storage services like Dropbox, SkyDrive, and Google Drive, Readdle's new Documents app for iPad could be worth a look. It's a free file viewer that plugs into the aforementioned services and also lesser known options like SugarSync, Box, and even private FTP servers. File compatibility is fairly robust; you'll be able to listen to music files, watch videos, and view (and annotate) PDF documents directly within the app. Microsoft Office files can also be loaded without a problem. But seeing as there's no shortage of file viewers readily available for iOS, the vast cloud integration Documents offers is what sets it apart. If nothing else, it's a tool that will help you stay better organized. Files can be copied and synced between various cloud platforms at will, and Readdle has also baked in iCloud support if you prefer Apple's own solution.
One file viewer with support for numerous cloud services
The PDF functionality proved particularly handy — Documents loaded some fairly large files without hesitation and its annotation tools worked exactly as we'd expect. It's unfortunate that you can't edit the content of a document, but there are plenty of options for that purpose in the App Store. There's also a buit-in web browser that lets you load and save web pages for later, but we can't imagine many people will abandon their tried-and-true Instapaper / Pocket workflows for this implementation. Still, other extras like optional password protection for files could at least make Documents by Readdle worthy of a quick download. It's free, after all.