To display emails on websites you can use the message archives option.
There is no "download as PDF" option directly from Envoke but there is a workaround:
First, view the online version of your email: Click the preview icon from the list of messages page.
In your browser select the Print... option from the browser navigation.
In the Print dialog window select the "Save as PDF" or "Print to PDF" option. This screen varies slightly between browsers but they will all have a "Save" or "Print" to PDF option.