I'd like to be able to pull in custom A attributes from CMS fields. 

Use Case:

To offer a PDF version of a course someone is going through (I have multiple courses, all via CMS), I'm trying to trigger an email opt-in modal to collect their address and deliver the correct PDF, based on the course they're currently reading. I need to be able to set a custom A attribute to show the correct modal, since each PDF will have its own unique modal (that is associated with a different form in Drip, my ESP). Right now, there's not a way to do this dynamically.