Why does free and voluntary trade increase wealth?

Free and voluntary trade is the basis of a capitalistic society where people are free to make whatever product they want. This increases competition.

If a person or company is able to innovate a new or improved technology that sets them apart from their competitors they would expect to sell more and create more wealth for themselves.

Thing about the pharmaceutical industry. If you find a drug that would cure cancer, you would expect to sell a lot of this drug because no one else has been able to do that thus far. If you are able to sell a product that no one has, you can charge a higher price and customers will still buy your product, thus creating wealth.