Yes! I don't like the taste of vinegar much so I prefer leaving it out but you can add it if you like. I do this in my preserving peppers recipe and you are welcome to check it out. For a gallon jar, you can add up to two cups of vinegar. Add the vinegar first, then add the brine, and when you are done, close the jar and give it a little shake to mix it all together. Then move on with the fermentation process the same way.