Word's graphic box is affecting text when printing to PDF

Summary: Word PNG graphics, with transparency, and placed over text (Layout = over text); PDF results in text distortion where the PNG graphic exists when printing to Adobe PDF.

Details: When we use a PNG image in Word and place the image over any text, there appears to be distortion when we print the Word document to Adobe print driver to create a PDF file.  The resulting PDF has a clear text-quality issue where the graphic box exists. The problem is evident when using a signature graphic in our Word docs and the signature sits 'over' the signature line with the name below it and it is visible on the resulting PDF. 

The distortion is evidently found at the border of the graphic image, but it does seem to distort text 'under' the graphic as well; but it isn't as obvious as when the graphic border sits mid-text.  I can recreate the problem any transparent PNG file. 

However, if you Save As an Adobe PDF (vs. printing to Adobe), the same exact document doesn't cause the text distortion. It appears limited to only the printer driver PDF creation process.  

I'm including visual examples as I think it'll make more sense when you see the results:

• PDF1 Image one; the text which is perfect after I used the 'save as' pdf option.
• PDF2 Image two; the same document was used to create this PDF, but I used the 'print' to Adobe method.
• PDF3 Image three; a different type of example showing a PNG graphic over general text... same issue. I highlighted where the Word graphic border exists to show the distortion point
• WORD1; a screenshot of the native Word document, showing how the graphic box is sitting 'on top' of the text, and appears to be the source of the PDF distortion.

Although we have one work-around, I am looking to have a better understanding of the cause, as well as a solution that will allow for both methods of producing a PDF document.