Hey David. Welcome to the group! Thanks for sending this in.
Like Toby said, there's not right now. There are only a few different content types available:
Simple Alerts: Linked image embedded in the Body, with CSV attached.
Advanced Alerts: HTML in Body with optional embedded image.
The reason I attach the CSV in a Simple Alert automatically is because (1) it's useful to know the exact data situation that triggered the viz (which otherwise might be lost, if your data changes by the time you get to checking the viz) and (2) I already have to pull the CSV anyway to see if the alert should be triggered, so it comes at no additional processing cost.
If the PDF version of the viz were automatically added to Simple Alerts, it would be mandatory, not optional--you'd get the embedded image linking to the Server viz, and the CSV and PDF attached. Also, it would be about double the processing and duration expense.
What's the use case you have for wanting PDFs? Is it that the entire workbook could be rendered and sent out all at once? If we only did it for the view in question, would PDF have any advantages over just the image?
Currently our Tableau reports can only be accessed by internal employees and not customers. So to get customers their reports we have our local field staff subscribe and then forward the email to the customer. They have requested a PDF format so I had to ask. I think they like that report format better than images pasted in an email even though its not really that different.