While Gnosis does not support attachments to the email itself, it does support attachments by link or button within the email content.
Step 1: Upload File To Attach
On the preview/setup screen of the communications item, click to Upload then select the desired file from your computer.
A message will appear and confirm the new link to the document has been copied to your clipboard.
Step 2: Paste File Link in Email Content
Open the Email Editor and paste the link as the URL for the desired text or button.
For more information on adding links and buttons into your email, please refer to the article on the Advanced Email Editor.