All the links are in one image which are linked to different pages. Why? Because the PDF X-3 is a good standard but it has a default compatibility with Acrobat 4.0, which does not support transparencies and lenses. Maintain OPI links maintains any Open Prepress Interface comments for linked images. Some people send images with 1800 dpi, 2400 dpi and more and this only creates much larger files, but does not increase the quality of the output.