From my quick view of your PDF file, the file contains cross-sections.
Typically cross-sections are drawn with a vertical exxageration so that small changes in the cross-section are plainly visible.
I would import your PDF and scale it to the horizontal scale. Jig your areas.
Since you are using 2009, and you want the area of the base course, use a field and apply the factor to scale that down.
For example, if your scales are 1"=100' H, and 1"=10' vertical, your areas are a factor of 10 off. (10 times the vertical distance)
If your base is area scale 100 sq. ft, then that section is actually 10 sf. (100/10 = 10)
An AutoCAD field allows you to apply the factor to your field easily.
Matthew Anderson, PE