You can attach an entire drawing to the current drawing as an external reference (xref). With xrefs, changes in the referenced drawing are reflected in the current drawing. Attached xrefs are linked to, but not actually inserted in, another drawing. Therefore, with xrefs you can build drawings without significantly increasing the drawing file size.
Attaching, Updating, and Binding External References
Detaching External References
Nesting and Overlaying External References
Reloading External References
Managing Xref Paths
Resolving Xref Errors
See Also
Using Symbols (Blocks)
Using Content Explorer