Here is a different technique I've discovered recently:
Press Option (Alt) and click in the vertical scroll bar, roughly where you want to go in the document, near the end or near the middle. You'll jump straight there. Without Option pressed clicking in the scroll bar will move you just one page. Using Option lets you jump much faster.
Another efficient method of skimming through a long document is using Command+F function - search. It works within Pages (opens search window), but it also works in most browsers. In Safari a little search window opens at the top, in Firefox at the bottom. Type in a key word, something you're looking for, and then click 'Next' or 'Previous'.