The High Energy cosmic-Radiation Detection (HERD) facility has been proposed as a main space astronomy payload onboard the China Space Station, with the aim of detecting cosmic rays (CRs) up to a few PeV and gamma-rays greater than 100 MeV. The instrument is designed to accept incident particles from its top and four lateral sides. Owing to its pioneering design, more than one order of magnitude increase in geometric acceptance is foreseen, with respect to previous and ongoing cosmic-ray experiments. The Plastic Scintillator Detector (PSD) constitutes an important sub-detector of HERD, particularly aimed towards photon tagging and precise charge measurements of incoming CRs, from protons to iron. Main requirements concerning its design include: high detection efficiency, broad dynamic range and optimal energy/charge resolution. The detector will be equipped with two layers of orthogonally oriented, short scintillator bars with trapezoidal cross-section, readout by Silicon Photomultipliers (SiPMs). In this work, an overview of the PSD project is presented, along with an illustration of its various design and readout aspects.