The United Nations Centre for Trace Facilitation and eBusiness (UN/CEFACT) provides a conceptual approach named Core Components for defining business document types based on generic, reusable building blocks. For facilitating interoperability in Electronic Data Interchange, these reusable building blocks are defined in an all-embracing manner. Accordingly, business partners customize the standard business document types for fitting their needs and requirements, resulting in different business document type variants. However, the approach is missing sufficient mechanisms for managing business document model variants. First, customizing standardized business document types is purely based on a textual specification. Second, the variability present within the Core Component approach lacks an explicit representation. In this paper, we aim at making variability explicit as well as adding a formal aspect to the business document type customization process by employing variability concepts from Product Line Engineering. Furthermore, based on having explicit variability models, business partners are provided with an approach for customizing business document types through configuring variability models.