This is a Pro only feature.
SketchUp must translate the elements within a CAD file into SketchUp entities when importing a CAD file. Supported CAD elements include lines, arcs, circles, polylines, faces, entities with thickness, 3D faces, and nested blocks. CAD layers are also supported.
SketchUp does not support AutoCAD regions, XREFs, hatching, dimensions, text, and proprietary ADT or ARX objects. These CAD elements will be ignored on import.
You can change any unsupported elements into primitive CAD drawing elements, within your CAD application, if you need to import these elements into SketchUp. For example, you can explode ADT walls and extrusions in Autodesk Architectural Desktop so they will import as faces in SketchUp. Some elements might need to be exploded multiple times in your CAD package to be translated into SketchUp entities.