If you want to send an announcement (email) to your Shareholders on Cake with an attachment, you can do this by adding the link to your Google Document (saved on your G-Drive and shared publicly) in the announcement.
Go to the Communication tab
Select New Announcement
Choose recipient (this can be a single shareholder or a group)
Select the link symbol and add the URL for the Google document you would like to share.
Choose the text you would like to be displayed ad select Add
This method will also work if you don't want your contacts to have to log in to Cake order to view the document - just insert the link into the text, and they can click it straight from their email.
Keep in mind, the emails will be sent from a no-reply Cake email address, it can be useful to add your email address in the text so that your shareholders know to respond directly to you.