Exporting high quality images from Tableau Desktop

The PNG files saved from Tableau Desktop are not intended for print use and don't scale well as they are bitmap files.  For printed materials created through Microsoft Office applications, instead export a vector version:

In the Worksheet menu, select Copy... (rather than Export...) and then Image...

Select the output options as with a normal Export

In Word/Powerpoint etc. insert the clipboard data via Paste Special - note this isn't available through the right-click context menu but can be found on the Paste drop down on the Home ribbon:

From the options available, select Enhanced Metafile - the image will now scale when enlarged and will print to a higher level of detail.