Sorry but my English is not good and I'm not sure to understand. This doc seem to explain that I can upgrade directly to the last version that's right?
yeah, rigth. just get autoinstaller from http://www.parallels.com/en/download/plesk83/,
# chmod +x autoinstaller_how_do_they_call_the_file
# ./autoinstaller_how_do_they_call_the_file