Mein Kampf, copies may be found in many used-book stores. 'Annotated' versions- whatever that means- are available. There is even a book, Cambridge Press, which gives a publishing history to 1980.
One is the Reynal & Hitchcock edition of 1939, and several subsequent re-printings, easily obtained at used book sources.

A fuller 'annotation' with all the bells and whistles is what is meant, with historical and social commentaries and digressions.

In print with several re-printings is one that addresses the history and background:
Mein Kampf, trans R. Manheim, Intro by D. C. Watt. Hutchinson, and reprint by Pimlico, London and Houghton, Mifflin, NY, etc. Watt was professor of International History, Univ. London; His 'Introduction' is detailed, "giving origins and history of the book, a critical assessment of Hitler's ideas and his understanding of political power."

Werner Maser, trans. R. H. Barry, 1970, "Hitler's Mein Kampf- An Analysis," Faber & Faber, was originally published in German.

Commentaries have been published in Germany, inc. Halbritter, Kurt, 1975, "Adolph Hitler's Mein Kampf, gezeichnete Erinnerungen an eine grosse Zeit," Carl Hanser Verlag.

There are many socio-historical works which go into the background of Mein Kampf.

I think a publisher is trying to use the copyright story in order to drum up interest in a new (his) edition.