'In essence, bleeds are stage 1 and packs are stage 2 of the pressurisation process.'
Otto Throttle. Bleeds & packs are one way of providing 'Air Conditioning', pressurisation does not always have to follow, on the ground or below 10,000ft for example you don't need to pressurise the cabin.
'Pressurisation' is achieved by controlling the rate that conditioned air leaves the aircraft. It relies on a flow of air into the cabin but does not have any control on that supply of air, only the release of it.