Ordinarily, it’s a good idea to keep the Reader menus visible so that they are available as you work. It is possible to hide them, using the View > Menu Bar command. However, the only way to display and use them again is by pressing F9 (Windows) or Shift+Command+M (Mac OS).
Reader also has numerous context-sensitive menus. These menus appear when you right-click/Control-click an element in the work area or PDF that has such a menu associated with it. A context menu displays commands that relate to the item or area that you clicked. For example, when you right-click/Control-click the toolbar area, that context menu displays the same commands as the View > Toolbars menu.