converting pdf file from RGB to CMYK

[Gumbare]

Hi there,
I'm trying to convert a pdf file generated from OpenOffice writer exported in RGB colorspace into CMYK colorspace. I need nice file process-print ready.
When I do: convert file.pdf -colorspace CMYK new_file.pdf
this command does the job but I loose so much quality that it's not acceptable.
The file itself is just black text + few black&white (grayscale) pictures so there is nothing colorful in it.

What am I missing or what should I do to convert that file properly - I repeat that I need pdf in CMYK?

greetings

[GreenKoopa]

My understanding:
PDF is most often used as a vector format. ImageMagick converts everything to raster. Therefore, your quality will go down and your file size up with your operation. A tool other than ImageMagick will handle vector formats better, although I have no suggestions. Set the -density to change the size vs quality trade-off. See http://www.imagemagick.org/Usage/formats/ for more information about supported image formats including PDF.

[Gumbare]

Thanks for your reply.
I just understood the difference between image and pdf file.
So you might be completely right that this is not a good tool.
I also found and learned about GhostScript. It has a nice tool for converting - ps2pdf (http://pages.cs.wisc.edu/~ghost/doc/svn/Ps2pdf.htm) but right now it's over my head with all these options.

I guess ImageMagick Forum is not good place to ask questions on GhostScript, isn't it?

regards