Hi Andrés,
The problem with \insertpages is that it inserts pages as layers, which means that header, footer and page numbers will be printed on it as well. That's what I don't want, and also your suggested link points to me to \insertpage in my case:
"Please note that the inserted pages will be placed on your ConTeXt pages like a new "layer", or floating object. This means that your existing headers, footers, crop marks will still be printed on top of or behind the inserted pages.
If you want to insert pages as completely independent pages between your existing ConTeXt pages, use\startpagefigure."
But the command \startpagefigure doesn't work as described on the wiki...