Brakes are suddenly hard to push since I put new pads on, why?

I recently put new front brake pads on my wife’s 2010 Chrysler Town and Country. I did not change the rotors as they were new last time I changed the pads and they still felt smooth and thick enough. Immediately after putting the new pads on the brakes are hard to press. They will stop but they do not stop as quick as they used to and the pedal is giving a lot more resistance than it used to. I don’t think it is the vacuum considering the change happened immediately after changing the pads. Could I have done something when I changed the pads that would have caused this??