Standardized business documents are a prerequisite for successful information exchange in electronic business transactions. The United Nations Centre for Trade Facilitation and eBusiness (UN/CEFACT) provides a conceptual modeling approach, called Core Components, used by Business Partners (BPs) for defining business document models (BDMs). These BDMs are essential for defining service interfaces in service-oriented systems. However, in such a highly dynamic environment with ever-changing market demands, BPs are confronted with the need to revise their BDMs resulting in new versions of BDMs. Furthermore, BPs may dictate the use of new versions of BDMs. However, small- and medium-sized enterprises (SMEs) may not always adopt new BDM versions due to the cost and effort involved, inhibiting electronic information exchange. In this paper, we present a framework for dealing with interoperability issues in service-oriented systems through providing BPs with Business Document Interoperability as a Service. Having such a framework at hand provides SMEs with a low-cost and light-weight approach for dealing with evolving market requirements and hence evolving business documents. Furthermore, we present a prototypical implementation as well as an evaluation of the framework proposed.