Save As PDF downsamples image

If I Insert Image from File, and do Save As PDF, how to get word to keep the exact same image in the PDF?  No compression, no conversion.

Currently, I start with an PNG image that is 1477 x 720 pixels.  The PNG image has the resolution flag set at 600 dpi.

When I save as PDF, I then open the PDF in acrobat, and copy the image, and paste the image into MS Paint.  The image size becomes 492 x 240.

Basically Word downsampled the image to 200 dpi.

I've tried every solution suggested:
-using the PDF or XPS add-on (same results)
-setting the Tools -> Compress Pictures... -> Options -> .. and unchecking the 'Automatically perform basic compression on save'.  (tried both clicking cancel and OK).
-adding key to registry HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Options\AutomaticPictureCompressionDefault  = 0
-tried saving through the Word interface as well as through C#.
-tried saving in C# using two different functions:

wrdDoc2.ExportAsFixedFormat("C:\\blah.pdf", Microsoft.Office.Interop.Word.WdExportFormat.wdExportFormatPDF, false,
 Microsoft.Office.Interop.Word.WdExportOptimizeFor.wdExportOptimizeForPrint, Microsoft.Office.Interop.Word.WdExportRange.wdExportAllDocument, 1,1,
 Microsoft.Office.Interop.Word.WdExportItem.wdExportDocumentContent, false, true, Microsoft.Office.Interop.Word.WdExportCreateBookmarks.wdExportCreateNoBookmarks,
true, true, false, m);

and

        wrdDoc2.SaveAs("C:\\blah2.pdf", Microsoft.Office.Interop.Word.WdSaveFormat.wdFormatPDF, m, m, m, m, m, true, m, m, m, m, m, m, m, m);

-tried printing using to 'Adobe PDF' printer using high res.  This works, but the file size explode because all the images are stored as the bitmap version and not the PNG version.
-I've also done the same experiment using GIF and JPG images, no better.

If I Insert Image from File, and do Save As PDF, how to get word to keep the exact same image in the PDF?  No compression, no conversion.