You can also send attachments in automated emails.
In Settings > Workflows, automate email external notification and document template to the same stage.
Important note: Both templates need to have same label.
Setup templates (email message and attachment document)
You need to setup an email template in the Settings > External Notification tab and also to upload your document (that will be sent with the email) to Settings > Document Templates list . Label them both accordingly with the same document label.
2. Assign templates to automation
After that go to Settings > Workflow tab, open the workflow you are editing by clicking on the title from the list on that page, pick a stage where you want this to apply. Hit orange “Automate” button (located at the bottom of each stage) and add both of these templates. When executed External notification will contain merged document as an attachment.
Clients will get it like this (message and attachment):
NOTE: It is possible to add multiple merge documents to be sent as attachment. You will just add multiple merge document templates with external notification to the stage.