Layouts Not Printing To Scale

[3-D Builders]

Hi, I'm new to this forum. I've been using CA 9.54 for about 2 years. I have yet to get a 24 x 36 layout to print to scale. I don't have a plotter so I export to .dxf and take it to a local blueprint shop that uses AutoCad. The prints always come out too small. (4'-0" = 3'-5") They have tried everything they know to correct the problem, but they say it's a Chief Architect problem.

How do I fix this

Thanks!!