Cloud printer allows you to print files from your iOS devices to your printer.

Cloud printer is an print application that allows users to print their documents with their iOS devices over the cloud. Some features are not yet implemented and will be added to Cloud printer shortly.
Cloud printer works over Cloud Print Service. Cloud Print service can connect to to any existing printer on Windows or Mac with Internet access that uses the Cloud Print connector within the Chrome browser.
Features:
* Print documents and email from different iOS devices
* Use iTunes to upload files so you can print its
* Use "Open in" menu to print a file
* Get list of available printers of account: status, name, properties of printer
* Stores list of printers in local storage of device
* Manage print jobs in queue
* Filter and remove print jobs
* Share printer

You can try it, please see the link below.
http://www.google.com/chrome/intl/en_us/p/cloudprint.html

Note: if you have an Cloud print ready printer (Epson, Kodak etc) or HP E-Print enabled printer you don't need your pc to be on, for other printers your pc needs to be ON.