As PZ said, the best way to do this would be with PHP. This is fairly simple scripting, and if you have the time it is a worthwhile skill to have. The easiest way to do this would probably be to set up a page with a form that links to the pdf. It would look something like this:
<!-- in form.php -->
<?php
if(isset($_RECEIVE['submit']))
{
$body = "Form downloaded by:\nName:\t" . $_RECEIVE['name'] . "\nEmail:\t" . $_RECEIVE['email'];
mail("contact@mysite.com", "Subject", $body);
header("Location: redirectToHere.pdf");
}
?>
<!-- the rest of the html including: -->
<form method="post" action="form.php">
Name: <input type="text" name="name" size="20"><br />
Email: <input type="text" name="email" size="20"><br />
<input type="submit" name="submit" value="Submit">
</form>
Should be that simple.
Nick
