[Lizard]

A few tips (not an authoritative answer):

Turn on rulers. (in the toolbar or command-R)
The ruler will appear just below the toolbar. On the right there's a drop-down labeled "Ruler scale". Pick something appropriate for your work (1 in = 1 ft maybe?) or type in your own.

Also, check out the Variables stencil -- it includes a couple options for automagically labelling shapes with their dimensions.