How to customize the PDF?

I'm trying to customize the pdf that the people that fill out this form can download. Is there any way to do that?

The pdf that is downloaded is basically a reflection of your jotform with the submission data inside it.

If you are trying to change it then the best thing to do is first view your submissions then enable the headers and texts which will display more than just the standard text on your jotform so that everything becomes visible to your users in the pdf file that is downloaded.