Inserts references to external files such as other drawings, raster images, and underlays.
The Select Reference File dialog box (a standard file selection dialog box) is displayed.
You can insert drawings (DWG), and DWF, DWFx, PDF, and DGN files. You can also attach point clouds (RCP and RCS files) using this method (not available in AutoCAD LT).
To select multiple DWG files for attachment, select Drawing in Files of Type. For all other file formats, you can select only one file.