Here is how you can do this.
So i have a flow that will trigger an approval with the PDF of email when ever i receive a new email in my inbox
So the first step is to trigger the flow and then export the email

The second step is to create an eml file and then convert it into pdf

The third is to use the converrted PDF file content in my approval action

This is how my overall flow looks like

Make sure you use the proper dynamic content as i am using in my flow to work in properly.
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Thanks,
Rahber