How can I attach a document from Google Drive
If you can see the document on your Mac, you could drag it into Agenda.
If you are on iOS, you could tap in a note to bring up the cursor, then tap the + button on the bar above the keyboard, and choose the paperclip icon. Choose the Files or Google Docs app, and locate the file in there, and attach it.
The last option would be to copy the web address of the Google document, and paste that into Agenda. It would take you to the Google site to see the document when you click it.
Hope that helps!