Technology, human and financial capitals will always be a significant constraint for manufacturing Small and Medium-sized Enterprises (SMEs). Keeping that in mind, this paper introduces a modular Smart Manufacturing (SM) Toolkit for SMEs as a set of technologies, methods, tools, and practices that can help manufacturing enterprises to increase their SM capabilities. The modular SM toolkit is composed of seven individual specialized toolboxes, which cover both technical and business management aspects of a successful digital transformation in a manufacturing SME. In addition, the various SME functions that can be supported with each individual toolbox are presented as well. The paper concludes with two short demonstration case studies as a means of an early validation mechanism for the SM toolkit in refinement.