I've taken your example code and tried converting half a dozen .DWGs to PDFs. Not a single one came close to looking like the .DWG image. The PDF file is saved, but not at all useful.
I am doing something wrong?
string dataDir = @"C:\Sandbox\Aspose\DWGTOPDF\";
using (Aspose.Imaging.Image image = Aspose.Imaging.Image.Load(dataDir + "9-0-0_01002R.dwg"))
{
Aspose.Imaging.ImageOptions.CadRasterizationOptions rasterizationOptions = new Aspose.Imaging.ImageOptions.CadRasterizationOptions();
rasterizationOptions.BackgroundColor = Aspose.Imaging.Color.White;
rasterizationOptions.ScaleMethod = Aspose.Imaging.FileFormats.Cad.ScaleType.None;
rasterizationOptions.PageWidth = 1600;
rasterizationOptions.PageHeight = 1600;
Aspose.Imaging.ImageOptions.PdfOptions PDFOptions = new Aspose.Imaging.ImageOptions.PdfOptions();
PDFOptions.PdfDocumentInfo.Title = "9-0-0_01002R";
PDFOptions.PdfDocumentInfo.Subject = "VAULT to PDF Tool";
PDFOptions.VectorRasterizationOptions = rasterizationOptions;
image.Save(dataDir + "output.pdf", PDFOptions);