Knowledge acquisition is an important part of any requirements engineering activity, as it builds the foundation for all decisions and actions performed. In PMI activities knowledge acquisition is equally important and more complicated as in requirements engineering in general. This leads us to the conclusion that PMI initiative should have an additional focus on the knowledge acquisition. This paper explores requirements elicitation for PMI as a knowledge acquisition process and proposes models for its accomplishment. It covers the following research steps - required characteristics of an effective PMI requirements elicitation are identified, corresponding existing research is analyzed, possible adjustments to the previously presented requirements elicitation model are identified, enhanced knowledge acquisition model is proposed, and the proposed model is illustrated with a real application example. As a result of this research the adjusted and detailed PMI specific knowledge acquisition model for PMI specific requirements engineering has been created that consists of two parts – the knowledge acquisition process model and the knowledge acquisition data model.