This a GUI for calling Ghostscript to change PDF versions. If you have older software that needs PDF files in say 1.4 format, but your PDF file is 1.6, this is your answer. Select your file, choose which version and convert it.
Requires Gnome 2.22.3 or better*, GTK 2.0 and of course Ghostscript.
* I haven't tested on newer version of Gnome.