How do i read documents on the iphone?

if i want to read maybe a word file on the iphone, is there a way i can upload it to the phone through an app of some sort? what im looking for is a way to maybe browse some documents on long commutes like on the buses or trains. what i do right now is read documents i mail to myself via my email on the iphone. it works great but its quite inconvenient and i want to do the same thing offline without any internet connection. is that possible? if so is it free?