This information can be found in the pamphlet included with your cartridge (or in the Products section of Ortofon.com). There are two specifications that you should pay attention to - Tracking Force Range and Tracking Force Recommended.  Tracking Force Range refers to the scope of weight that can be applied to the cartridge while still maintaining proper playback.  Tracking Force Recommended refers to the optimal weight which will result in the best combination of groove holding and sound.  Deviating outside of the Tracking Force Range may result in undesired operation, and therefore should be avoided.