How to join several pdf's files in just one

Thanks to Pablo Iranzo for send me that line:
gs -q -sPAPERSIZE=a4 -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=out.pdf $* it is usefull to join several pdf's files in just one.

Imagine you download the book Linux Kernel in a Nutshell (which is a good idea if you wanna learn things about Linux kernel ). That book is free offered in multiple pdf's files, but you want to send it straight to the printer in just one step and without blank pages, you'd better got a single pdf file.