All pressure canners can be used as pressure cookers, but not all pressure cookers can be used as canners. To determine if your pressure cooker can be used to can, first look at the instruction manual. If there are directions and timing for canning, then it can be used for canning. If you lost your manual, the standard given by the U.S. Government is: that your pressure cooker be equipped with a canning rack, and be large enough to hold to hold at least four quart-size (one liter) jars. This might include 8 quart or 7 1/2 liter pressure cookers and above – depending on the shape and size of the manufacturer.
According to The National Center for Home Food Preservation, Pressure cookers have less metal, are smaller in diameter, and will use less water than pressure canners. The result is that the time it takes a canner to come up to processing pressure (that is, the come-up time) and the time it takes the canner to cool naturally down to 0 pounds pressure at the end of the process (known as the cool-down time) will be less than for the standard pressure canner. The come-up and cool-down times are part of the total processing heat that was used to establish USDA process times for low-acid foods. If the heat from the come-up and cool-down periods is reduced because these times are shortened, then the heat from the process time at pressure alone may not be enough to destroy targeted microorganisms for safety. That is, the food may end up underprocessed. Underprocessed low-acid canned foods are unsafe and can result in foodborne illness, including botulism poisoning, if consumed.
Canning is a precise science, not an art, and is beyond the scope of this website, right now. So follow the instructions at the recommended websites, below, for specific canning instructions for your pressure cooker.
I recommend you visit the following websites for more canning information.
National Center for Home Food Preservation: Canning in the Pressure Cooker