In general, if you're looking for a PDF of a scholarly article or book, you might find it through academic databases like Google Scholar, ResearchGate, or institutional libraries.
While the text itself is a brilliant beginner’s guide, it is highly recommended to study it under a qualified teacher or alongside a reliable sharh (commentary). The question-and-answer format leaves some room for nuance, especially regarding the Names and Attributes of Allah, where scholarly differences exist. Ar-risaalah Al-mufeedah Pdf
Often available at regional Islamic bookstores like the M.I Nana Islamic Store or Al-Huda . In general, if you're looking for a PDF