iPads can natively print to network printers...so long as the printer supports airPrint. The list of supported devices
is pretty long. If your device is on the list but doesn't show up when you attempt to print, it could be that you just need a firmware update to add support.
However, all is not necessarily lost if your device doesn't natively support airPrint. Lantronix, maker of all kinds of niche network devices, has their xPrintServer line. It also only supports specific devices, but the list if very long. The HP list
is very long and includes devices going back to the LaserJet 4 (released in the early 90's).
New xPrintServer devices are very expensive, but they can be found easily on eBay for reasonable prices. I have one on my network for a couple of Brother and Xerox printers that don't natively support airPrint. The device is so easy to setup that all that's required to make it work is connect it to an ethernet port and then power it up. It truly is that simple. It automatically finds any printers on your network that it can support and they will show up on your iOS devices as available printers. It has a web interface, but there's also an iOS app that can be used to manage it (the iOS app will just find it on the network so you don't need to know the IP of the device).