Yes, you would need a PDF4me Subscription to start using Workflow. Currently, the Workflow access is free as it is running on Beta mode.
Soon we will introduce a Pricing plan that will best suit our users along with an updated version of the feature.
PDF4me is a constantly evolving document management tool. Our mission is to discover the best ways to improve PDF4me and add new features to help our consumers. We would love to collaborate with you all in this mission.