There's a built-in media system that allows you to upload files. But having control over viewing permissions is a different matter, and if you wanted them to be browsable in the front end that's a whole extra UI to build.
But, I'm currently working on a module that makes handling different kinds of media a lot easier. You could upload word documents and get a "Binary Media" item that you could then just use with the built-in ContainerPart/ContainablePart to generate lists
of download links. Something else I've got in the works will allow giving users rights to specific items; there's nothing otherwise at this time that I'm aware of.
The media garden project is at: http://orchardmediagarden.codeplex.com
It's not quite production ready but it's not that far off, upload / import / display media works for a number of formats already. Give me a shout if you need any help :)