While the full textbook is a copyrighted product from Difusión, there are several ways learners typically access it:
Legal "free" content is typically limited to sample units and supplementary materials provided by the publisher or authorized distributors: aula internacional plus 3 pdf free
The "Plus" version is the updated edition of the classic Aula Internacional series, specifically designed for Level B1 learners. : Modern topics and vocabulary. While the full textbook is a copyrighted product