I see the answer for printing from an iPad to a Windows enterprise, but I just want to print from an iPad Air to my home printer (HP Officejet Pro L7590) that is running on my network from a Windows desktop. Is there a solution simpler than Presto?
The L7590 does not provide Airprint capabilities and can 't be added.
If you run Windows you can try to enable AirPrint - like described here (I haven't tried it my self, because I'm running OS X, so I can't comment on how good it is): http://www.airprintactivation.com/ - then the printer(s) setup on your PC will be available in iOS
If you run OS X you can download a more less free AirPrint enabler: http://www.netputing.com/handyprint/ - then the printer(s) setup on your Mac will be available in iOS
The HP Officejet Pro L7590 is not AirPrint enabled, however you can print to it using the HP ePrint app.