Check out how to solve the “You must have the Microsoft Save as PDF or XPS Add-in for 2007 Microsoft Office installed to send documents.” error.
“You must have the Microsoft Save as PDF or XPS Add-in for 2007 Microsoft Office installed to send documents.” – Microsoft Dynamics GP Community
Install, Upgrade & AdminMicrosoft & the GP Ecosystem
Archived post from 2014. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.