1. OfficeSuite Pro
OfficeSuite Pro has won our last two Android office suite shootouts, and for good reason: It's hands-down the best fully featured office suite available for Android users.
OfficeSuite Pro costs $15, but don't let the price scare you: You get what you pay for. The program boasts an elegant design on both smartphones and tablets and is jam-packed with advanced desktop-like functionality for documents, spreadsheets, and presentations. It integrates with numerous cloud storage services and, as of the most recent release, offers native PDF-markup commands.
If you want to use your Android device for productivity, OfficeSuite Pro is the first app you'll want to install.