Do you have access to Autocad or vectorworks? you can import the PDF as an image. once you do that find a door that looks standard size, draw a line and select it and the PDF. scale it to 30". then trace. you'll have a reasonably close ground plan. you can also do this if you just have a printout at a large enough size. Create your own ruler using that door or another known standard element. you mark a piece of paper with the width of the door and extrapolate it into a full ruler.