Is it possible to print documents directly from the iPad models or do they have to be transferred to a computer first?

Officially, upon the unveiling of the original iPad, Apple stated that to print a file from any of the iWork iPad applications -- whether it was Pages, Numbers, or Keynote -- you needed to "send it to your computer via e-mail, iWork.com public beta, or File Sharing in iTunes."

However, with the release of iOS 4.2 for the iPad on November 22, 2010, Apple added "AirPrint" capability that allows one to officially print directly to a number of compatible Hewlett-Packard printers.

Even better, though, the third-party eCamm Printopia (for Mac) and Collobos FingerPrint (for Mac and Windows) make it possible to share printers with all iPad models running iOS 4.2 or higher.

eCamm describes Printopia with the following:

Whether you have an inkjet printer plugged into your Mac, a laser printer plugged into your router or even a network printer, if your Mac can print to it, Printopia will share it. Is your printer plugged into your AirPort or Time Capsule? No problem. Printopia translates for your printer, allowing it to speak to your iPhone or iPad even if it's not an AirPrint-compatible printer. Printopia even supports many password-protected printers.

Collobos, likewise, explains that with FingerPrint:

All your printers are displayed in an easy to read list in FingerPrint's main window. You can then select which printers you want to AirPrint enable. Bonjour technology is used to advertise your printers, and in seconds those printers will show up in your iDevice.

Printopia is available for US$9.95 and FingerPrint is available for US$7.99 for the Mac version and US$9.99 for the Windows version.

For those interested in free options, AirPrint Activator is a Mac OS X application that makes it possible for any shared printer to be visible on an iOS 4.2-powered iPad as well. This application is made available for free, but the author is accepting donations. If you find the application useful, it is highly recommended that you make a donation to support its continued development.