You will need to set up a database first. Then, using PHP, connect to the database.
Then a form using method="post" to send the input fields to the database.
Pseudo code would be something like
if email and name are true
and if email is not already in the database
then download pdf
else echo "please enter your name and email address";
Maybe someone could properly write it. I'm pretty new to PHP syntax but I get the logic.