Tinknocker, Hvacmarie are correct. The only thing that causes pressure is the 'vapor', expanding. More vapor = more pressure, less vapor = less pressure.
Bama, Hvacguy, Beenthere: The heat absorbed is what causes the liquid to boil into vapor which then creates pressure.
The compressor suction only allows the refrigerant to boil at a lower temp, but does not have anything to do with the amount of pressure produced.
BB: The capacity of the compressor is only concerned with how much volume can be 'pumped'. Again, nothing to do with suction pressure. The capacity will change with the temp of the suction vapor, but not the pressure.
Someone correct me on this one if I am wrong.