To maximise effective use of screen real estate, it may be desirable when presenting documents in fullscreen mode to rotate the pages by 90 degrees so that the contents appear upright when the screen is placed on its side. This is best done before entering fullscreen mode:
Select all pages in the page list and rotate them left or right as appropriate.
Set the view to Fit Width (command-0).
Set the view to display Single Sheets and turn of Continuous for the best experience. (You may also prefer to turn off Page Breaks, since the page shadow will be incorrect when the screen is on its side).
These command can also be issued when in fullscreen mode, using the keyboard shortcuts. If the page list had focus when fullscreen was entered then all pages can be selected with command-a and rotated with the left or right rotate command.