page backgrounds

[Thomas A.Schmitz <thomas.schmitz@uni-bonn.de>]

These are my first forays into the unknown territories of Metapost. The 
following code is copied verbatim from the matafun-manual:

\startuniqueMPgraphic{copyright}
picture p ; p := btex COPYRIGHT etex rotated 90 ;
setbounds p to boundingbox p enlarged 1pt ;
draw p withcolor .8white ;
currentpicture := currentpicture
xysized (\overlaywidth,\overlayheight) ;
\stopuniqueMPgraphic
\defineoverlay[copyright][\uniqueMPgraphic{copyright}]

\setupbackgrounds[text][rightmargin][background=copyright]

But I don't see anything. The log shows that metapost calculated a 
background, but I don't see anything. What am I doing wrong?

Best

Thomas