of course you can, you can use many keywords as you want, but of course there many thing to consider!
I think you can rank high for many different keywords. But for that, you will have to really work hard. I suggest you build backlinks with different keywords in the anchor text.
You might want to try PPC. This will take little effort and can get you to the top of the search engines for an unlimited amount of keyterms (assuming you have the budget and it is cost-effective for your business/web model).