Hi John M,
Microsoft .WMF format. [.WTF?] is pretty good in the resultant PDF. However, when you zoom in to the PDF, the curves get a bit rounded-polygonal, in a smooth-bumpy way. Odd - not a huge issue unless people zoom in. However, it is evident if they print it. And they will.
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Also, I've been silly, even mentioning DPI/PPI in this thread.
That should have no bearing whatsoever on how the graphic appears onscreen - only on how it prints. 150, 300 or even 600dpi will make no difference to the quality of the onscreen presentation.
Basically, what matters is the number of pixels in the graphic. And there are plenty of those!
John