Updated September 15, 2017 Double-click on the PDF floor plan to open the PDF file. Locate the key for the scale of the floor plan. Note that the key usually looks like a long line representing a foot on the floor plan, similar to the key on a map. Hold a ruler over the line and mark the length of the line on the ruler. Measure the floor plan with the ruler, noting how many times you use the line measurement. Note that if you use the line measurement twice, then the measurement equals 2-feet (if the key indicates the length of the line is equal to 1-foot).
