Or do I need one specially made for canning?
You need a pressure canner. Depending on what you are canning you can use a water bath canner. Pressure canners are important for meat and for almost all other vegetables, like carrots, squash, green beans, squash, corn, okra, etc. Pressure cookers don't keep enough pressure for canning. http://www.foodsafety.wisc.edu/consumer/fact_sheets/pressurecannerandcooker.pdf
Some pressure cookers are adjustable and can be dual-purposed, but generally I agree with SKK, you want to ensure that you're achieving the right pressure for anything that isn't sufficiently acidic to prevent the growth of bacteria.
Most pressure cookers designed for cooking are not big enough to accomodate pint or quart jars.
When canning with a pressure cooker, make sure that you ALWAYS use recipes that have been approved by the USDA, such as the Ball Blue Book. They can give you insight on if you have a pressure cooker that is appropriate for canning.