A common request from users has been to provide a quicker method to change a document’s unit of measure. Previously, the only out-of-the-box method was through the Document Properties window, which involves a whole series of clicks and mouse movement. In SolidWorks 2012, units of measure can now be changed via a pop up menu in the status bar (bottom right of the SolidWorks window).
Of course, more refined control is still available in the Document Properties. This area is now easy to access as one of the options in the unit of measure pop up menu.
(If your status bar is hidden, you can display it going to View pulldown menu>Status Bar (near the bottom of the list)