This module for Silverstripe CMS embeds an external user guide document (such as Google Docs) in the CMS and provides a link to it.
composer require "somardesignstudios/silverstripe-user-guide"
Add the user guide document embed code in your yaml configuration:
Somar\UserGuide\Admin\UserGuideAdmin:
embed_code: '<iframe src="https://docs.google.com/document/d/e/<GoogleDocID>/pub?embedded=true"></iframe>'