Don't you love the way Linux has evolved. I needed to combine few pdf files into one and was looking for a pdfedit kind of thing with capabilities for combining multiple pdfs and 
this guy from 
Ubuntu Geek provides the steps clearly.
sudo apt-get install gs pdftk
gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=
 -dBATCH   ...
Simple, isn't it!