Why do I still get jagged edges when printing some files in x8.

Most of the time my designs print pretty good on my Epson p800.  Every now and then a new design will print with parts of it having jagged edges. When zoomed in on the screen,  it looks great at any magnification.  I'm not too computer savy, but I have been working with Coreldraw for 6 or 7 years, most recently on x8. I have read other similar complaints,  but I'm kind of stumped.