Disc Brakes Are Too Hard?

I recently had someone replace the shoes pads on my Chrysler 300M. It has 4 disc brake. Anyway, he replaced the pads but now the brakes are very hard, harder than they used to be. The car stops fine but I think this person might not have done something right. I read some where that you must drain some brake fluid out first... this person did not do that. I guess my question is how to I fix the hard brakes and what exactly happened when he compressed the pistons without draining fluid?