Each indexed page has own PR. PR is then calculated on base of inbound links (sum of inbound links PRs). PR is ranged on base of logarithm of 5. But if your links is going from page with 20 links (for example) you will get only 1/20 of page PR. For page with only 1 link will work this: 5xPR1 inbound links -> PR2 5 PR2 or 25 PR1 -> PR3 5 PR3 or 25 PR2 or 125 PR1 -> PR4 But real sites have much more then 1 link on page, so there will be required much more links to acquire PR.