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
- PDF files with more than one page are attached one page at a time; DWF files are attached one sheet at a time; and DGN files are attached one model at a time.
- You can drag underlays directly into the current drawing.
- You can reattach an underlay multiple times, treating it as a block. Each underlay has its own clip boundary and settings for contrast, fade, and monochrome.
- If the underlay file contains layers, you can control how the layers display after attaching the file.
- External references (xrefs) attached to a drawing can include underlays.
- You can view DWF and PDF underlays only in the 2D Wireframe visual style. DGN underlays can be viewed in any visual style.
- Hypertext links from PDF files are converted to text.
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.
- You cannot attach the file until you have entered the correct password.
- You will be prompted for the underlay file’s password each time that you open the drawing.
- If the drawing has several password-protected underlays attached, you will be prompted for multiple passwords.
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.