Place it as a drawing.
File>External Content> Place External Drawing.
You can place the scan or other drawings type into all but the 3D window in archicad or directly onto a sheet in the layout book.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"