After more research, this isn't possible.
I'll create one dashboard with all of the combined data and then generate alerts and PDFs.
Not possible out of the box.
However, as a quick workaround, create a 5th dashboard which is the combination of all four dashboard and generate PDF alerting for 5th dashboard.
After more research, this isn't possible.
I'll create one dashboard with all of the combined data and then generate alerts and PDFs.