Perhaps more than any other topic, printing from a mobile device gets to the heart of how mobile devices differ from desktop-based computers. If you use a desktop-based computer, look around at the cables; they are everywhere. Most long-time computer users have a carton of old cables stashed away somewhere. Cables are not cheap, and users often keep old cables around so that they have them on hand in case they need another one. When the need arises, you search out the carton, and upend its contents to find the FireWire cable, the USB cable, the serial cable, or whatever. (Of course, in that entire carton, you have every type of cable except the one you need.)
With the advent of efficient and relatively inexpensive cordless connectivity, you can toss out those cables. Along with those cables, you can toss out the dust and dirt that always accumulate in that rat's nest of cables behind or under your desk. What people are relying on today is the ability of devices such as computers and printers to communicate directly over the Internet. When you can send a print job via email to your printer (or to a colleague's printer halfway around the world), cables do not matter that much any more. (Of course, things such as security do matter so that you do not receive junk print jobs from halfway around the world.)
This standardization on Internet communication protocols is a large part of what has made mobile devices possible. It takes some getting used to the idea of connecting a printer to a computer through the Internet, particularly when the devices are sitting right next to one another, but the gains in productivity can be tremendous.
Along with the standardization on Internet communication protocols, the world is moving more and more toward the use of cloud computing and data storage that, like your printer, might be located a continent away. You can use mobile devices the way you have always used computers, but experiment with the new technologies to see what you can do.
As you experiment with these technologies, you will come to see why some of the initial complaints about mobile devices such as iPhone and iPad are irrelevant. The clamor for USB ports, serial ports, and special connectors ignored the movement toward these standard protocols.