[RobertKD]

If all you want to do is scale a room and furniture to see how you can re-arrange the placement and orientation of tables and chairs, this is all do-able. but you will have a slight learning curve first until you get confident with the package.

What you want to do is scale a room, very easy

scale tables and chairs very easy, group the table and chair objects then you can copy them and populate the "room" you can even make them into your own stencils future use.

So I'm going with hat Andrew said try it, Omnigraffle is a lot more then meets the eye,...