In the world of RGB and the internet, compression is a necessity. We use it to make files easy to transport. In the world of printing though image quality means everything.

As you can see in the first image, excessive jpg compression has been used, this has made the file smaller but it has seriously deteriorated the quality of the image.

In a printing scenario CMYK images should be saved as either TIFF or EPS files which ensure that compression is not used and the image is reproduced at the best possible quality. The bottom image shown on the right is more suitable for printing.

If you are saving as a TIFF you must also ensure that LZW compression is not used as this will also give you the same problematic result.