Not sure I understand, but the simplest solution to me is to create an HTML email, with a link to a web page on your website, and on that page put a link to the pdf that you've uploaded to the server.
this is also simplest for me. But they don't want the person receiving the email to have to click anything at all. Just receive the email and read..
I read about this mix of HTML and JS. [ ] Works
<html>
<head>
<title>PDFObject example</title>
<script type="text/javascript" src="pdfobject.js"></script>
<script type="text/javascript">
window.onload = function (){
var success = new PDFObject({ url: "sample.pdf" }).embed();
};
</script> </head>
<body>
<p>It appears you don't have Adobe Reader or PDF support in this web
browser. <a href="sample.pdf">Click here to download the PDF[/url]</p>
</body>
</html>