Pam has a nice overview of Doc Attach for all GP versions at:
#GP2018 Feature of the Day: Document Attach Unplugged – Microsoft Dynamics GP Community
#GP2018 Feature of the Day: Document Attach Unplugged – Microsoft Dynamics GP Community
Tips & Hidden FeaturesMicrosoft & the GP EcosystemGP 2018
Archived post from 2017. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.