InvoicePrinter is a Ruby library for generating PDF invoices, with additional CLI and HTTP server interfaces. It takes structured invoice data (as Ruby objects or JSON) and generates formatted PDF documents using the Prawn library. The system consists of three main components: the core library for PDF generation, a command-line executable for direct use, and a server executable providing a HTTP API. The architecture shows good separation of concerns with distinct modules for data models, PDF rendering, font handling, and server interface.