Adobe Illustrator CS4
PDF (adobe.com)
Importing, exporting, and saving
Importing files
About linked and embedded artwork
Place (import) files
Links panel overview
View and save metadata via the Links panel
View file information about linked or embedded artwork
Update modified links
Restore a single missing link or replace link with a different source file
Set placement options for linked artwork
Embed a linked file
Unembed or relink an embedded file
Edit original artwork