AFAIK the Multipage Export is not working properly at least since V6 or 7.
I've managed to install it but the result was not really good.
You have to order the pages yourself in a list and then, the export often
broke in the middle of the process.
I have asked people at XWiki how to do it and the
Hello,
I'm trying to use the Multipage Export Application
(http://extensions.xwiki.org/xwiki/bin/view/Extension/Multipage+Export+Application).
I've tried to install it as the readme.txt supposes but as on the webpage
described its latest version is validated for xwiki 3.1 to 4.1.
I updated to 9