though you might meanwhile have solved the problem, here's another suggestion how to improve the image quality. First of all I found that your images delivered in the sample file have a resolution of 70-something dpi, which as far as I know is a little low for printing. When you export your charts to png or eps you should be able to set the resolution somewhere. Try to use at least 300 dpi. With this the eps-files will become huge, but the exported pdf will still have a decent size. To convert the png to eps I used "convert file.png file.eps" in the shell / terminal. It's pretty quick and leads to good results.
Regards, Katrin
