Hi,
Not all PayPal accounts supports PayPal Pro. You can follow this tutorial which explains how to get all the information for the PayPal Pro plugin:
www.putler.com/support/faq/how-to-get-pa...gnature-information/
Regarding PCI DSS, it means that with PayPal Pro, the credit card information passes through your website. Because of that, you need to have a SSL certificate setup on your website and activate the "force SSL on checkout" option of the configuration once it is setup. The best is to ask your hosting company to set it up for you.