Are you saying that the picture of the chart exhibits the jaggies after converting to a PDF using Pub 2010, or are you saying that it develops the jaggies within Publisher after you close and reopen the Publisher file?
Assuming the second you might get better results if you save your Excel charts as 150 - 300 dpi .PNG images and then insert them into your Publisher page as a non-linked image at 100% scale.
You can try saving the chart as an image from Excel to your local drive, or if you have inserted it already into Publisher and it is not yet showing the 'jaggies', then select it > right click > save as a picture > choose 150 or 300 dpi .PNG and save the
image to your local computer where you can find it. Then create a new picture box and insert that new PNG picture of your chart. Right click it again > format picture > Size tab > make sure the aspect ratio is locked and the scale is 100% or less.
While this image will not be linked and will need to be updated if you change the chart it should look better.
DavidF