-Adequate documentation is critical for successful implementation, maintenance and further developments of product configuration system (PCS) specially in companies making complex and highly engineered products. This article is based on experience of modelling and utilizing a PCS from an Engineer-To-Order (ETO), where the main focus is on the challenges concerned with the documentation of the PCS, both in the development and production phase. Aligning the development of the PCS with an automatic documentation system creates value. Using the suggested method for documentation facilitates the following activities: (1) iterative testing of the system during the development, (2) communication with domain experts, (3) documentation and maintenance, and finally (4) updates without spending a lot of time and resources. This article is supplemented with a case study from an ETO company where the method for the automatic documentation was developed and tested.