You can import, attach, or open files, other than DWG files, that were created with other applications into your drawings.
A DWF (Design Web Format) file is a highly compressed file format that is created from a DWG file. You can attach a DWF file as an underlay to a drawing file. By attaching a DWF file, you can reference it without increasing the drawing file size.
DXF and DXB files are two types of drawing interchange files used to transfer data between various applications.
You can attach 2D geometry stored in a MicroStation DGN file as an underlay, a reference for additonal work.
You can import MicroStation. V8 DGN drawing files into DWG files.
You can view and manipulate raster images and associated file paths in drawings.