An icon to access the sort menu would make the interface a little easier to use. Context meus are nice, but they should be a shortcut to an action rather than the only way to trigger it.

I also noticed that the search box only searches document titles. It would be nice to have it filter document titles as you type, and then perform a full-text search when the user hits enter (like Google's online Drive search).

Awesome app, keep up the good work!

Ah. Yes, that was precisely what I was looking for. It wasn't very obvious though, so you might want to add some more visual ways to make the user aware that the option exists.