Creating PDFs from Word Documents. Black showing around images when printing.

I create word documents for work that include images.  These images are sometimes pngs.   I save the word doc as a PDF and when some people receive it, they go to print and the transparent areas of the pngs fill with black.  I am able to print these same documents just fine, but for others they cannot.

I have stopped using pngs and use just jpgs now and that seems to work.... But this issue seems to be happening now on PDFs created over a year ago (and not originating in Word).  

Is there a work around to get the item to print as it appears?    I have looked at various posts in this community and cannot quite find the answer to my question.