Is it possible to use itextsharp to convert postscript to pdf? If there is no other way to do this in .net?
Converting PostScript to PDF is called "distillation." iText and iTextSharp do not support distillation. Ghostscript will be your only FOSS solution.
You can use Ghostscript, as he explained here:
http://hi.baidu.com/lqyidxa_igfv/blog/item/df2037b394539fa0d9335a94.html