Hello Rob,
I believe the OOTB PDF service broker and the SmartForms PDF controls were designed to generate a PDF file from a SmartForms or URL; and as such you will likely not be able to target this email. One thing that can be done is perhaps surfacing the content of this email in a SmartForms also, and as such you can use the PDF SmartObject to target this SmartForms URL and generate the PDF.
That makes sense...but do you have any idea how you would surface that content in a smartform? I'm not seeing an immediate way to do that.
I assume the email template have to look a certain way and is pulling data back from a SmartObject data source; if so:
1. Perhaps a View/Form can be designed to mimic this email in its design
2. It will have some parameter to accept IDs
3. When the Form/View initialize, you would pass in these IDs and and call the appropriate SmartObjects to load these data
4. If this is all working and the View/Form loads the data and looks likes the email
5. Perhaps call the PDF Converter SmartObject in the workflow and pass it the URL (the IDs can be passed in a parameter and will dynamically tell the form which data to load) which will create a PDF of this Form/View containing the data
6. Then you can use the PDF File SmartObject to retrieve this PDF and add it to your imaging system