After one year the Pro “Internet” Version will expire if not renewed, however, the free version will still work (1-Site | 1-Form). Subscriptions can be renewed at any time, or even purchased for up to 5 years.
Alternatively, the Intranet Version will continue to work after one year, only the support and updates will expire. The Intranet Version requires PDFtk to be installed on your WP server.