Through Notebook Types and Templates you can attach documents (turned in to templates) under the Notebook Type Templates:
Add the attachment documents as templates - for each one
Click Options and then click Manager.
Click Documents and then click Template Maintenance.
Select the Template Type from the list in the middle column.
In the right-and column, Click the ✚ button and select Add Template.
Enter the Template Name (name of the document).
Tick Merge if the file needs to be merged).
Add any Notes required.
Fill an any other required information (Picklist suppression, Start and End date).
Click Save.
Now click the 🖉 icon on the new template entry to create the document content.
Add a new template (attachment document) to the email template
Click Options and then click Manager.
Click Documents and then click Notebook Types and Templates.
Select the Notebook Type (if you need to create a new Notebook Type see below).
Click Notebook Type Templates.
Click ✚ (right hand side of Notebook Type Templates line).
Select the Template for the attached document.
Click Select.
Add a new Notebook Type
Click Options and then click Manager.
Click Documents and then click Notebook Types and Templates.
Click the New (
) button.Type the Notebook Type Name.
Select the Notebook Folder this will be stored under.
Select the new Item Template.
Supply a Notebook Subject.
Tick if this applies to Candidates or Contacts.
Click the Save (
) button.