Why two formats of the Third Edition? PDF books have many advantages. They can be downloaded right away and easily stored on the computer. They are searchable to some extent, although nothing replaces a well-curated index. (Yes, the third edition has such an index.)
However, research shows that deep reading is done best with printed text. The publisher International University Line offers both formats of the book so that readers can choose the one that suits them best. I hope this makes the book as accessible as possible.
The pdf is available directly from the publisher. The print version can be bought on amazon. While I am no fan of amazon, their platform is the most expedient way for the book to reach an international readership.