Request to include site Context information with the DWG that is part of the PDF.
Typically there are 2 options:
1. Bind Xrefs
https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2020/ENU/AutoCAD-Core/files/GUID-5BF89799-D496-4AAD-8773-9D4BF9B9E8CD-htm.html
Or,
2. eTransmit
https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2020/ENU/AutoCAD-Core/files/GUID-413A58AD-C86F-432F-A4AC-A2737237001A-htm.html
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O’Brien & Co Design Build Technology
www.obrien-co.com
Source: Autodesk