AirPrint is a great feature introduced in iOS 4.2. As advertised by Apple, you just need to open, tap and print. No software or driver is required. Your iPhone can automatically search for AirPrint-enabled WiFi printer around and you can print the document, email, web page or photo right away.
However, there is a catch. Not all printers are supported. As of now, AirPrint only works with certain models of HP printer such as HP Envy e-All-in-One series and HP Photosmart Plus e-AiO. If you’re not owning any of those, AirPrint is useless even your printer supports WiFi.
Thanks to Intelliborn. The company has developed a hack called TruPrint that enables AirPrint on unsupported printers (e.g. Epson, Canon, Brother).