How do you link an email to a PDF file?

I have two problems I'm trying to figure out, both related to the link between an email and a PDF file.
(1) We have a couple of standard notices, such as the "Move Out Receipt" and the "Rental Rate Increase Notice," that are linked to the email for past due notices. Every time we want to send out one of these notices, we have to be sure to change the subject line and the body of the email, otherwise the tenant will receive a message entitled "Collections notice from Highwest Storage," which wouldn't be good! The PDF file that's attached to the email is correct. It's just the email that's wrong.
How do I correct this?

(2) I want to set up a *new* email with a *new* PDF file attached to it, and send it to all of our RV tenants. The email is to announce an increase in our dump station fee, and the PDF file is a list of reminders while using the dump station. How do I do this?

I appreciate the help!