private Ghostscript.NET.GhostscriptVersionInfo _version = Ghostscript.NET.GhostscriptVersionInfo.GetLastInstalledVersion(Ghostscript.NET.GhostscriptLicense.GPL | Ghostscript.NET.GhostscriptLicense.AFPL, Ghostscript.NET.GhostscriptLicense.GPL);

using (var raster = new GhostscriptRasterizer())
{
    raster.Open(fileStream, _version, false);
}