A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
Sorry, I can't duplicate the result you describe with the file you uploaded. Using Insert>Picture>Picture from file or pasting the picture brings it in at the normal resolution.
In PowerPoint for Mac, you can choose File>Compress Pictures and set Picture Quality to High Fidelity (Maximum ppi). This has exactly the same effect as setting the analogous option in PowerPoint for Windows. I recommend you do this as a first step when opening a presentation from your client.