The search for a PDF version is driven by practical needs:
: Try to immerse yourself in the language as much as possible. Listen to Japanese music, watch Japanese movies or TV shows, and try to find native speakers to practice with.
Minna no Nihongo is published by (and distributed globally by various publishers like Bonjinsha). Freely distributed PDFs of the full textbook are unauthorized copies. Sharing or downloading these files without payment violates copyright law in most countries. The Japanese publishing industry is strict about such infringements, and linking to pirated material would be irresponsible.
Buy the physical CD-ROM version from Amazon Japan. This disc contains a license for a digital PDF plus all audio tracks. You can install it on your computer legally.
The search for is understandable. The book is essential for anyone serious about reaching intermediate Japanese (N4 level). It provides the clearest explanations of keigo , causative-passive, and conditionals.