Sorry ciro, but i like write tex code.
  1. save following code as test.tex
    %%
    %% save it as test.tex
    %%
    \setupcolors[state=start]
    \starttext
    \dorecurse{660}%
    {\startTEXpage[width=3cm,height=2cm]
    \vbox to \vsize{\vss
    \hbox
    to\hsize{\hss\framed[width=2cm,align={middle,lohi},background=color,backgroundcolor=green]{p.\tfd\recurselevel}\hss}\vss}
    \stopTEXpage}
    \stoptext
  2. create the pdf
    $>texexec --pdf test.tex
  3. Save the following into my-imp.tex
    %%
    %% save as my-imp.tex
    %%
    %% \setuplayout
    \starttext
    \centerline{%
    \externalfigure[test][page=1]
    \externalfigure[test][page=3]
    \externalfigure[test][page=5]
    \externalfigure[test][page=7]
    \externalfigure[test][page=9]
    \externalfigure[test][page=11]
    }
    \blank[1cm]
    \centerline{%
    \externalfigure[test][page=2]
    \externalfigure[test][page=4]
    \externalfigure[test][page=6]
    \externalfigure[test][page=8]
    \externalfigure[test][page=10]
    \externalfigure[test][page=12]
    }
    \stoptext
  4. create the pdf
    $> texexec --pdf my-imp
    
    
        
  5. the first page of my-imp.pdf now has  12 pages from test.pdf;
Now, if you have yourfile.pdf you can replace
\externalfigure[test][page=8]
with
\externalfigure[yourfile][page=8] etc.


\externalfigure has parameters page,width,height, etc...;
you can use it to scale to appropriate dimensions (they depends by size of paper);search on wiki for externalfigure


Usually i make simple scripts that create my-imp.tex with correct pagenumber (ie the pagenumber that i want to select); also i use \clip (search on wiki) to correct some page and pdfinfo to have some informations on pdf files.

But hans also replay with a quick and clean solution.....


luigi