How Do I Scale Drawing With No Obvious Scale, But Looks Like It Has One?

Help! I Was Given A Drawing In Acad To Change For A Simple Renovation Project. I Wanted Exact Sizes So I Put The Origin At The Corner Of The Plan View; However, The Distances All Measure 1/2 Smaller Than I Need. In Other Words, When I See A Distance Of 12 Feet, Acad Reads It As 6 Feet. How Do I "force" A Scale Here? Do I Set Up My Scale First And Then "paste" The New Drawing Into It?

do the 6 feet meaasurements come when you add a dimension or when you use the DIST cammand? Each has a different solution.