If you want just to use the PLS methodology with no need to pay for a license, you can use cran R project or octave. Otherwise, you can just look for a trial version of any available PLS software
As miguel Gonçalves said, there are many other ways to use the PLS method... Try this software that has a free version for students, in which you can do many multivariate analyses, like PLS, very simply. It is called Infostat and it is an Argentinean software, which has an english version available. You can download it from
www.infostat.com.ar
What is interesting is that you don't need any programming knowledge to use it!