You can print to Apple AirPrint compatiable printers. A current list of AirPrint printers can be found here: http://support.apple.com/kb/ht4356
You will require a minimum of OS 4.2 on your device and at least version 5.0 of the app.
To print in documents: press the spanner (wrench) icon on the toolbar and choose Print. The orientation of your printing is determined by the orientation of the device at the time.
To print in spreadsheets: swipe to the second page of the toolbar and press the printer icon.