How could I set up a pay and download with paypal?

I want to sell book at my website.

How could I ask the visitor to pay through paypal and then the download option will be available to the paid client? Or is there any other program doing that?

 

You can do it using Buy Now Button.
Or use any third party sites like E-junkie or Payloadz.

 

I set up the buy now button several times, however, after the payment, it just gives a confirmation page. I need it to redirect to a download option.

So once people pay, they can download the file.