Buyer beware
This app is a waste of money and is rather misleading. First things first. It only lets you print from your photo library. No doc printing (at least not very easily).
Second. It was near impossible to even select a photo to print and it hardly ever recognized my inputs. This app is garbage. Save yourself the money and just download the free official gmail app and print directly from there (you can set up google cloud print within Chrome browser only at he moment). Once you have set up and shared your printer you are good to go.... For free.
Sonburn about
gCloud Print, v1.0.3