There is no "official" printed documentation for program MARK - the canonical documentation is (in effect) the MARK helpfile.
However, MARK is a large, complex program, and in general it is not an application that can be learned by simply browsing the helpfile. To aid new users, there are two main sources of secondary documentation which you should consult prior to using MARK.
Novice MARK users
For 'novice' users (and this is a broad category - it could apply to 'complete neophytes to analysis of marked individuals', or 'people with some background', but who have not previously used MARK), a 900+ page (and growing) online book "Program MARK: A Gentle Introduction...", co-edited by Evan Cooch & Gary White is the recommended starting point. Reading this book (or, at minimum, the 'core chapters') is strongly recommended as your first step in learning to use MARK.
Experienced MARK users
For more experienced users of MARK (or equivalent software), lecture notes from a course co-taught by Gary White and other faculty at Colorado State are available in electronic book format. These notes provide a somewhat more rigorous technical background to using MARK. The Cooch & White book (above) covers some of the same material, but focusses more on how to implement the procedures using MARK, rather than the details of the underlying theory.
In addition, there is also an unmoderated online forum devoted to issues concerning using MARK, and related software. This is your primary source for 'support' when using MARK.