About Attaching Files as Underlays

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. 
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

  1. 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. 
  2. You can drag underlays directly into the current drawing. 
  3. 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. 
  4. If the underlay file contains layers, you can control how the layers display after attaching the file. 
  5. External references (xrefs) attached to a drawing can include underlays. 
  6. You can view DWF and PDF underlays only in the 2D Wireframe visual style. DGN underlays can be viewed in any visual style. 
  7. Hypertext links from PDF files are converted to text. 
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. 
  1. You cannot attach the file until you have entered the correct password. 
  2. You will be prompted for the underlay file's password each time that you open the drawing. 
  3. If the drawing has several password-protected underlays attached, you will be prompted for multiple passwords. 
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. 
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