For people who might use the iPhone and iPad to get work done, these devices were born with an annoying defect: the inability to print. Apple addressed this shortcoming in iOS 4.2 with AirPrint, which gave iPhones and iPads the ability to print iWork documents, Microsoft Office documents, RTF documents, PDFs, images, and text files to AirPrint-compatible printers over Wi-Fi. AirPrint discovers compatible printers using Bonjour, then converts the document to PDF to create the print job. It's a clever way to accomplish printing without turning iOS into a bucket of print drivers.
But of course there are drawbacks. Not all document formats are supported. Because iOS knows nothing of the target printer's features, you get only the most basic print options -- namely, how many copies and whether to print one-sided or duplex. You can't choose paper size, or between color and black and white, for example. You get the defaults. Depending on the app, you might be forced to print the whole document. Some apps allow you to choose a single page or range of pages, and some apps don't.
Perhaps the biggest drawback is that AirPrint is new, and your printer is probably old. Fortunately, there is no shortage of third-party solutions -- for homes, large networks, and in-between -- that leverage a Mac, PC, Windows server, home router, or stand-alone appliance to make virtually any old printer AirPrint-compatible. At least one -- EFI's PrintMe Mobile -- even brings AirPrint to Android devices.