Certainly is a better place to write here (i have had written this in Beta). A forum in Germany laments the bad pdf export from the designer. Gradients in vector graphics are frayed. Enlargements (here somewhat exaggerated) show clearly. In my attempt I found out that one does not have to export a pdf, but only an eps format. If you click on an eps in the Mac, the preview is automatically converted into a pdf, which then shows a best quality and does not deteriorate with a new import into the designer.
The image shows up the pdf export from AD, below an exported eps, which was then opened as a converted pdf in the designer. The differences are very clear. I hope you can incorporate the detour through the preview in the program. Sorry for my bad english