API integration plus sales of watermarked documents

WordPress/WooCommerce website to sell two products. One is via a partner API (documentation available) and the second is several document bundles where each page is dynamically watermarked with details obtained from the payment gateway (Plug-in for this has already been identified). We have a preference for the front end of the website to be developed locally for ongoing support needs. This project may just be for the harder coding aspects, but we are open as to how far the Freelancer can take our project. This is for a new website.