If you do any sort of document editing from your phone, there's a good chance you've needed to print something at some point. Or maybe you need a quick copy of an image and don't want to go through all the trouble of transferring it to your computer and then printing. Or maybe there's some other scenario that I can't think of right now when you've needed to print something from mobile. No matter the situation, printing in Android has always been sort of a pain in the ass.
In KitKat, however, Google has added native printing capabilities as part of the package. The printing framework will be able to communicate with local printers over Wi-Fi or with any printer in a Google Cloud Print account, making printing a breeze from basically anywhere. Users will be able to modify most of the basic parameters, including paper size, pages to print, and which printer to send the document, image, or file to.
Printer manufacturers will also be able to use newly introduced APIs to develop their own print services, which will allow for printer-specific options to be to handled directly from Android. Developers will also be able to use new APIs to add printing capabilities to their apps "with minimal code changes."
From the look of it, printing will be accessed via the action bar, but it isn't entirely clear how it will work past that. However, according the Android Developers site, the printed object will first be converted to PDF as that's the primary file format Android will use for the service.
So, yeah. Printing from your mobile, quickly and painlessly. Sounds convenient.