How to define email template that allows me to attach a document from the lead instead of a attachment for all leads.

How to define email template that allows me to attach a document from the lead instead of a attachment for all leads.

For email templates, is there a way to add a variable to an email so that it attaches a document associated with the lead when an email is sent?  Based on what I see, I can only attach a single file that gets used for the email template.  I would like a specific email template to be sent for each lead.