Normally on the Mac when you click on the scroll bar, it scrolls up or down by just one page. In big documents this can be pretty annoying. If you want to make a big move, you either need to click a bunch of times in the scroll bar or grab the scroll bar and move it all the way to where you want it.

But there is another way. You can change the behavior of what happens when you click in the scroll bar so that when you click it moves you all the way to that place in the document, in a single click. To set this go to System Preference and select the Appearance preferences. In there you'll see a section called "Click in the scroll bar to:". If you select the "Jump to here" option instead of the "Jump to next page" option, you'll get this new behavior.