First, "electricity and magnetism" is a common topic in physics, covering EM theory. "K. K. Tewari" is the author's name, so they might be asking about a PDF related to a book or research by him. "PDF upd" probably stands for "updated PDF". So the user is looking for a blog post that discusses Electricity and Magnetism by K. K. Tewari, with an updated or newer PDF version available.