I'm looking a free eBook reader for Windows 7 having capability to convert mobi to PDF format.
Calibre does that - and lots more;
For any book in your Calibre library just right click->Convert Books->Convert Individually (or bulk but here's instructions for individually).
A dialogue will pop up:
Just select PDF for output format over at the top-right.
There are lots of options but you can just use default and usually get a reasonably output. Click OK and it'll convert in the background.