If you have an HP, some models will work but it's limited. However, you can make any printer work by using a couple of apps.
First one you need is PrintNshare from the app store this must be running on your iPad to work. If your printer is wireless, the setup is fairly easy and should sort you out.
Other apps include WePrint which works when the PC is on if you have no wireless on your printer.
Email me if you need more info!