c# acrobat pdf convert to Image (export Image)

Hi

I want to extarct image using acrobat sdk.(Single page pdf to image)

I found the code and test that.

My problem is I don't know the size (mm) of the document.

Code is

string fileName = "C:/.../.../test.pdf";
Acrobat.AcroPDDoc pdfDoc = new Acrobat.AcroPDDoc();
bool ret = pdfDoc.Open(fileName);
            if (ret == false)
            {
                throw new FileNotFoundException();
            }

            int totalPage = pdfDoc.GetNumPages();
            int currentPage = 0;
            
            Acrobat.AcroPDPage pdfPage = 
            (Acrobat.AcroPDPage)pdfDoc.AcquirePage(currentPage);
            Acrobat.AcroPoint pdfSize = (Acrobat.AcroPoint)pdfPage.GetSize();
            Acrobat.AcroRect pdfRect = new Acrobat.AcroRect();
            
                    
            pdfRect.Left = 0;
            pdfRect.right = pdfSize.x  ;     
            pdfRect.Top = 0;
            pdfRect.bottom = pdfSize.y;

            MessageBox.Show(Convert.ToString( pdfSize.x) + Convert.ToString( pdfSize.y) );
            
            pdfPage.CopyToClipboard(pdfRect, 0, 0, 100);


            IDataObject clipboardData = Clipboard.GetDataObject();
            Console.WriteLine(Convert.ToChar ( clipboardData));
            if (clipboardData.GetDataPresent(DataFormats.Bitmap))
            {
              Bitmap pdfBitmap = (Bitmap)clipboardData.GetData(DataFormats.Bitmap);
              pdfBitmap.Save("C:/.../.../.bmp");

            }

then Message Box show pixels of x,y . And DPI(dot per inches) is changed.

I want to extract it to the actual size of the document. Or Is there DPI function in interop.Acrobat?