About Attaching Files as Underlays

You can attach a DWF, DWFx, DGN, or PDF file as an underlay to a drawing file.

You can reference and place underlay files in drawing files the same way as you do raster image files; they are not actually part of the drawing file. Like raster files, the underlay is linked to the drawing file through a path name, which can be changed or removed at any time. However, you cannot bind an underlay to a drawing and you cannot edit or modify the underlay’s content.

By attaching underlays, you can access files in your drawing without greatly increasing the drawing file size.

Note: Although underlay files are reproductions of their source drawing, they are not as precise as drawing files, and they will show slight discrepancies in precision.

Special Considerations

Tip: You can copy selected objects from a DGN underlay file into the current drawing with the NCOPY command.

Password Protected Underlay Files

A file that you attach to a drawing as an underlay can be password protected. DWF, DWFx, and PDF file passwords are case sensitive.

Note: The ability to add passwords to AutoCAD files has been removed because this feature does not meet contemporary security standards. You will continue to be able to open password-protected files.