Instead of hunting for an elusive "official" Manabou Nihongo PDF, to find individual skill-specific worksheets. Combine 2–3 different PDFs from trusted sources (e.g., one for particles, one for te-form, one for counters) and create your own study set.
If you have spent more than a week searching for high-quality Japanese self-study resources, you have likely encountered a term floating around forums, Reddit threads, and language exchange Discord servers: manabou nihongo pdf