In order to get a button to point to that PDF, you would first need to upload your PDF in the “Media” area of your Dashboard. Once it uploads it will create a URL for it. After you do that, you can go to the page you are editing and set it up. You would insert a “Button” module, and paste the url to the pdf in the area that opens when editing the button module. If that doesn’t make sense, let me know and I will try to explain it better or walk you through it. I would recommend setting it to open in new tab. That is also an option under the Link area of the Button Settings.
After I typed this, I noticed that it looks like you already have the PDF uploaded. The button to the right links to it.