I think you can print them from lego.com. At the bottom of the web page, under customer service you will see building instructions..then you have to enter the police station code 7498.
Go to the Lego website and you can download a PDF of instructions under Customer Service. You will need the 4 or 5 digit number associated with the set, and it cannot be a really old set. The following link should get you there as well. http://service.lego.com/en-us/buildinginstructions
lego.com can send you anything you've lost. We were up at the Lego store at Downtown Disney and told the gal that we lost the pieces to build a figure. She directed us to visit lego.com
Once there, scroll down to the bottom of the page, see under CUSTOMER SERVICE and click missing parts or in your case click BUILDING INSTRUCTIONS.
Hope this helps! (It's free too!) If you need pieces, they will send them free of charge.