[kirkmc adds: Several points. First, in Column View, you need to have Show Preview Column checked in the View settings. When you select a PDF, its first page shows in the Preview column. From there, you hover your cursor and see two arrow buttons. You can either click on these or scroll.
This might be useful if you just need a quick glance at a file, but once you've selected the PDF, you can view it in Quick Look by pressing the space bar, which lets you see the document at full size.]

