For my reference (and yours if for some reason you can’t find the same articles I found), here’s how you print from an iPad to a shared Windows Printer on a Windows Server 2008 R2 Machine using Apple AirPrint and some cmd magic.:

1. Install the app from this page
2. Do the stuff at this page, sans the iTunes stuff
3. Open the 2008 R2 firewall Control Panel
4. Right click on Bonjour Service, click Advanced tab, and check all three checkmarks (Domain, Public, Private)
5. Create a rule for the AirPrint.exe file from step 2 to match the Bonjour Service on step 4.
6. Print from your iPad
7. Profit.