Unfortunately, PDF Generator does not support msg files natively. As msg is a compressed file, like zip, you would have to create your own component to unwrap the msg file to html or rtf files, plus any attachments, and then submit each file to PDF Generator.
In addition, you would have to implement some processes on LiveCycle to handle the conversions.
I do know of a component which interacts with PDF Generator to convert msg files to pdf.
Hi I am looking to do the same thing, let me know what you end up implementing.