Printopia for Mac OS X will now enable you to Airprint to any printer that is connected to your Mac from your iPad, iPhone or iPod Touch running iOS 4.2.
Printopia also has the feature of a virtual printer, allowing you to save print-outs to your Mac as PDF files.
Printopia will work with pretty much any setup you have for your printer. Whether your inkjet printer is plugged into your Mac or a laser printer plugged into your router or even a network printer, if your Mac can print to it, Printopia will share it.
Even if your printer is attached to your AirPort or Time Capsule its not a problem for Printopia as it translates for your printer, allowing it to speak to your iPhone or iPad even if it’s not an AirPrint-compatible printer.
Via Tipb