Thanks "fodiator" for your contribution.

I agree with user "ubuntu21" about that
little mistake. I 've fixed it by copying the file to split into tmp folder:
mkdir tmp
cp "$1" tmp/ <---my modification after line 26 of the program
cd tmp
pdftk "$1" burst
It is also very important to check that you have all the programs required
[ pdftk, pdftops, poster, epstopdf] installed in your linux box (deep search in Synaptic or Aptitude to be sure).
I did it in this machine: Ubuntu 10.04 LTS - Lucid Lynx (pretty outdated nowadays).
Your script works great splitting pages in landscape A4. After using your program I managed to print the copies in "booklet" style with Adobe Acrobat. The results are great and I couldn't have done it without the help of this forum.