Discrete-event systems have gained a lot of interest due to their wide range of applications. SDES is a unified description for stochastic discrete-event systems. The aim is to use this description as a basis of a new multi-formalism modeling framework. In this paper, we introduce PDETool, which is based on SDES description. This modeling tool provides features for construction and translation of models into the XML-based input language of an SDES-based simulation engine that is developed for this purpose. Currently, we have implemented some useful extensions of Petri nets, such as stochastic Petri nets (SPNs), stochastic reward nets (SRNs) and stochastic activity networks (SANs) in this framework. PDETool is easily extensible to support a wide range of graphical and non-graphical formalisms. Furthermore, it facilitates the construction, animation and simulation of models. This tool has some advantages over the existing multi-formalism modeling and simulation tools, which will be mentioned in this paper.