You can use the secure socket connection for creating a pdf at (notice the https protocol):

<a href="https://pdfmyurl.com/?url=google.com">A pdf to download</a>

If you copy paste that into your website html editor, then you get (go ahead, try and click it!):

A secure pdf to download

Note: this will not work for the domain www.pdfmyurl.com you must use pdfmyurl.com as the domain, or you will get a security certificate popup warning.