%output=pdf
\setuppagenumbering[conversion=numbers, location=]
\setupheadertexts[pagenumber][][][pagenumber]

\starttext
\startpostponing[+2]
\page
\noheaderandfooterlines
%this will generally be a fullbleed picture or set of pictures on a
page by themselves
\framed[frame=on, width=\textwidth, height=\textheight]
{\dorecurse{1}{\input zapf}}
\page
\stoppostponing

\dorecurse{20}{\input davis  }
\stoptext
