Complex sentence: LeapFrog sells several different packs of paper, often in conjunction with a related programming cartridge; the paper may include special instructions to the pen or cosmetic alterations to reflect the subject for which it is intended.
Split into simpler sentences: LeapFrog sells several different types of paper with which the pen may be used, often in conjunction with a related programming cartridge. The paper may include special instructions for using the pen, as well cosmetic alterations to the paper reflecting the subject for which it is intended.