OK, I am a newbie . Please be nice.

I am trying to set the scale of a sheet to 1/4 = 1'. I want every object I draw to use that scale so that when I export to PDF the scale will follow and I can measure objects on the sheet with adobe and they will be correct. Example: I draw a box that I want to measure 24'  x  16'.  How to I set this in options?

Seems like this should be easy, but I can't seem to get it right.