JPEG

JPEG file encoding is a form of "lossy" compression. The image quality drops as the file size goes down. For printing it is generally advisable to avoid the JPEG format whenever possible, however if you want to use it, you should save your files at the highest possible quality. Many of our customers find that any amount of degredation is too much and stay away from the JPEG format, however sometimes you may be supplied a file in this format and sacrificing storage space by simply changing it to a larger TIFF or EPS won't help the output quality. However, if you have to open it and re-save it, do not save as JPEG again; repeatedly compressing an image will lead to rapid and drastic degredation.

Save your format as Baseline.

Make sure the color mode is CMYK, not RGB or anything else.