[NTG-context] viewerprefix

[jbf]

Hi list,

I have successfully managed to get a vertically-oriented page number in 
words in the margins, but NOT with the number prefixed by the word 
'page'. I thought I would be able to do this by adding viewerprefix=Page 
(mentioned on the wiki for \setupuserpagenumber) but it gives me no 
result. Any thoughts on how I can achieve this? As I say, everything 
else works except the desired prefix.

Current MWE:

\def\mypagenumber#1%
{\inframed[frame=off,leftframe=on,rightframe=on,orientation=90]{#1}}

\setuppagenumbering[alternative=doublesided,location=margin,command=\mypagenumber]
\setupuserpagenumber[numberconversion=words,viewerprefix=Page]

\starttext
\input Knuth
\stoptext

Julian