Chipotle chiles, especially in adobo sauce (e.g., here), give an excellent smoky flavor. You should be able to find these in your grocery store in the Mexican section.
Pressure cookers and pressure canners are the same thing; with the canners being larger, and often having a pressure dial. Both can reach the same pressures and therefore temperatures if designed and manufactured correctly
The pressure canners dial gauge is more accurate for adjusting for food types and altitude, as you can get exact numbers not just 10 psi and 15 psi as with typical weight regulated pressure cookers. But for low acid foods you need 15 psi anyway
Pressure preserving is done because of the higher temperatures reached. This saves time and energy, and some food react better to a short 250°F (120°C) cook that an long 210°F (100°C) cook
Pressure preserving high acid food is worth doing as long as the food does not deteriorate quicker due to the high temperature (some soft fruits will)
For preserving low acid foods you need a known good pressure cooker that can reach 15 psi (103 Pa) and therefore 250°F (120°C)
With a commercially published recipe that has been acid level tested, you will have a published time that will be safe. For a home-made recipe you have to take the worst case scenario for the acid level of the main content, and cook for that. Your local government health department will most likely publish tables for this that you should be using. Remember to use altitude adjustments for timings too
Just relying on adding a teaspoon of vinegar or lemon juice per jar is not a safe and scientific method for raising the acid level, though many people do it, and have not come to any trouble with it?
You pressure cooker should come with a manual that confirms what it can or cannot do. Download a new copy if this has been lost
Also see What kinds of pressure cookers are there, and what are they good for?
Best Answer
You cannot preserve just any salsa recipe (unless you're just freezing it).
Tomatoes are on the border between acidic and non-acidic foods. What this means is that they can be water-bath canned if they are sufficiently high in acid; but, if they are low in acid, they need to be pressure canned.
If you want to be sure to avoid trouble, follow a tested recipe. Salsa recipes will have a careful balance of low and high acid ingredients. Do not alter the proportion of acids (tomatoes and vinegar or lime/lemon juice) and low-acids (other vegetables, peppers, etc).
The recipe you choose should specify if it requires pressure canning or water-bath canning. One of those two methods must be used, though... you can't just put it in jars and save it.
For tested recipes, see the Ball Blue Book, the Ball website, or the National Center for Home Food Preservation.