How do you change the logo and the size it is displayed the PDF invoice and PDF packing slip?

Just as further information, the logo I am using is 200x200 and in jpeg format (doesn't work in tiff ot gif says not supported!).
 
It loos great on the HTML invoice but on the pdf invoice it is about twice the size it should be.
 

Hello Brian,
  
If you want use gif or tiff images you can use PDFlib based library.
  
Actually we use the same size when adding it on HTML and PDF page. Is it possible see your PDF file?
 
Thanks,
ViArt Support Team