There are a number of options available to the ADOBE READER as to the format of the document.

The 2 global options are

• full screen - without any of the MENU buttons appearing along the top or the side
  
• normal [ default ] screen - in which the page size is somewhat smaller so as to enable the menu buttons

As a General rule - the pages will open in FULL SCREEN mode. The CTRL+L key will allow you to toggle between the 2 formats.
ESC will also move you out of FULL SCREEN MODE.
Adjustments to the page size can also be accomplished through using the CTRL+1 / CTRL+2 / CTRL+3 set of keys.