All the content pages that are visible on the event's website (except for forms) can be shared in the Engagement app with the participants.
To see these pages, go to the Content tab of the Engagement app. You will see two tabs: Published and Unpublished. Unpublished pages are hidden from participants, and the published pages are the ones you already shared with participants.
Please note: for a page to be visible in the Unpublished or Published tabs of the app, it needs to be published in the website builder first.