2
In the Show/Hide group, check Thumbnails to enable the thumbnail previews.  
Now, to navigate through your document, you can click on a thumbnail image to jump to the desired page.
3
Click on a thumbnail image 2 to jump to page 2.  
You can also increase or decrease the size of the display. By increasing the pane size you can see more pages on screen simultaneously.
4
Click on the right side of the pane and keep the mouse button pressed and drag it across towards right hand side so that the pane size would increase.