"PDF Drive" is a search engine that scrapes the web for PDF files. While it offers easy access to thousands of documents, using it for copyrighted textbooks like Minna no Nihongo comes with significant caveats: Minna no Nihongo Review - Tofugu
: This is the most reliable "permanent" home for older editions and some newer scans of the Shokyu (Beginner) and Chukyu (Intermediate) series. Reddit (r/LearnJapanese) minna no nihongo pdf drive 2021