Show PDF file after submission

I am interested in showing users a PDF file after they complete the submission of a form. I could redirect them to the path of the PDF file after submitting, and I could also attach it to an email sent to them upon submission, but I am wondering if anyone knows of a way that they can see the pdf ONLY after submitting the form. i.e. they cannot see the PDF by simply entering the URL of it without submitting the form first.
Maybe this can be done with some sort of cookie?
Does anyone know if this is possible?
I tried googling and I cannot find an answer….

My last resort would be to show a code or password in the success message or email which can be used within the pdf file to show the content. But I figured I would ask in case anyone knows an easier way for the user….

thanks.

Caleb