After compiling the tree, or after installing the binary distribution you
can get man to recognise the XFree86 man pages by adding 
/usr/X11R6/man to
the MANPATH in /etc/default/man, the line should 
look similar to:
    MANPATH=/usr/man:/usr/X11R6/man
MANPATH environment variable if you do not want everyone to access the
man pages.
By default the man pages are compressed using ``compress'' to
conserve space.  If you do not want to compress the man pages change
CompressManPages to NO in your ``xf86site.def''
file.  Those using the binary distribution can use ``uncompress''
to uncompress the man pages.