If you’ve got a print job on your hands and you need it as soon as possible, but all the printers on your network are often busy, you can pool these printers together so your document will automatically print to the first available printer. Just go to the Printer Setup Utility (in the Applications folder, within the Utilities folder), Command-click on all the printers you want to pool together, then go under the Printers menu and choose Pool Printers. A dialog will open where you can name your pool (the default name is “Printer Pool”), and it shows a list of printers that are in that pool.
You can click-and-drag the printers into the order that you want and then click Create, which adds a new printer in your Printer list called Printer Pool. Choose that as your printer, and then when you choose Print, Mac OS X will start looking for the first available printer.