You can attach a DWF, DWFx, DGN, or PDF file as an underlay to a drawing file.
You reference and place underlay files in drawing files the same as you do raster image files so they are not actually part of the drawing file. Like raster files, the underlay is linked to the drawing file through a path name. The path to the file can be changed or removed at any time. By attaching underlays this way, you can use files in your drawing without greatly increasing the drawing file size. You can only view DWF and PDF underlays in the 2D Wireframe visual style. DGN underlays can be viewed in any visual style.
Note: Although underlay files are reproductions of their source drawing, they are not as precise as drawing files. Underlays may show slight discrepancies in precision.
You can use OSnaps with Underlay files.
If you have created or received a PDF file to use in CAD, you can attach it to your DWG file – here is how…
1. Open the Attach dialog box by going to the Insert Tab
2. Select the file you want to attach by first changing the file type
Then select the file you want and hit Open.
3. It will then open the standard attach file dialog box. You can select options as you choose.
It comes in as a PDF Underlay.