Yes but you have to be aware of a number of things. First of all, there is no way on GM vehicles to know how much refrigerant is still in the system unless all of it is recovered, then a measured amount is pumped in. If the system is overcharged it is possible for liquid refrigerant to slosh into the compressor and destroy it. They can only pump vapor which can be compressed. If refrigerant has just leaked out slowly, which is to be expected after 14 years, add one can at a time then see how the system works. If it's acceptable, leave it alone. More is not better. If the compressor is already running but it's not blowing cool air, you have some other problem and adding more refrigerant may create an entirely new and more serious problem.
Most importantly, professionals wear gloves, safety glasses, and face shields. Escaping refrigerant can cause frostbite and blindness.
If the can feels cold and has condensation forming on it, the refrigerant is turning to a vapor and is being drawn into the system. If the can doesn't become empty within a couple of minutes, place it upright in a pot of hot water.
Be sure to use R-134, not the older R-12 and definitely not any of the "environmentally-friendly" alternatives. Most shops now have refrigerant identifiers to find systems that have been contaminated with these aftermarket products. They will refuse to do any work on your system if those products are found because it will contaminate their recovery and recycling equipment.