The first solution is to e-mail document and print them from there.
The second solution is to build printing into the OS and to download only the exact driver you need by looking at what kind of printer you have via bonjour. Which you will need a wireless printer for.
A USB solution is less convenient then e-mailing the document therefore it's not needed.
But if you need the wireless solution built into the OS I wouldn't hold my breath.
There are several printing apps on the app store which are meant to work with the iPhone, but all the ones I have tried (most popular ones) didn't work (and I don't care if they worked for you).
Apple should build it into the OS and tie it tightly in with printer vendors - so the drivers are download directly, but as of now they haven't done this.
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The way printing on the iPhone SHOULD work. You have a contextual option called "Print", when you tap it for the first time it goes through a super-quick setup process to download the driver for this particular wireless printer directly from the vendor. You can subsequently printer every time at that location from then on. Same goes if you try to print at someone else house or the office. If their printer is a different model you go through the driver process again.
This is the way it's SHOULD work. But it WON'T. When it come to this kind of stuff Apple are historically very lazy.