The design and evaluation of Product-Service Systems (PSS) constitute a challenging problem due to its multidimensionality. This challenge becomes bigger when the PSS customization is required, within the new manufacturing paradigm of Industry 4.0. Nevertheless, the literature work regarding the customization of PSS and the PSS investigation within the Industry 4.0 is rare. Towards bridging these gaps, the present research work proposes a methodology for the quantification of PSS customization complexity, considering Industry 4.0 aspects. The proposed metrics are validated in different product-service scenarios.