Online upgrade is practically automatic. You just have to enter the upgrade's payment code and the email address you provided when buying it, and PDF2XL CLI will do the rest on its own: connect to Cogniview's server, authenticate the details, and upgrade itself.
PDF2XL CLI will download the required data for the upgrade, and display a progress bar, and when it's done it will apply the upgrade automatically and display the following screen:
Online upgrade may fail if your computer is behind a firewall or not connected to the internet, or if the payment code and email address you entered are incorrect. In any case of error, don't hesitate to contact firstname.lastname@example.org for help.