The page rank that displays on the toolbar (also known as the foolbar) is only updated a few times a year, but the changes you do today will start affecting your position in the SERPs once your pages are indexed and cached with the change, the PR is there but it doesn't show on the foolbar.
I liked that "foolbar", you can copyright this term ;-)
In order to increase your toolbar PR you have get quality backlinks. Quality backlinks are from relevant websites and if possible an authority website.