If anyone ever needs to convert a pdf to postscript on Windows here's a... sneaky, free and arguably legal... way do it -
http://tech.gluga.com/2012/07/conver...n-windows.html
In this instance one would concatenate the 20 .ps files (copy 1.ps_2.ps+...20.ps all.ps) before the pushing combined postscript (all.ps) into the ps2pdf converter.
BR