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While many shoes have a little give for stretching, especially if made from leather, this give isn't much more than "breaking in" the shoe to fit you properly. There isn't enough give to change from one shoe size to another. Also, given the fine shaping of dress shoes, they are often less forgiving with stretching. If the shoes feel too tight, try another pair. For all their glamor and fashion, these shoes are the least comfortable of the bunch. They concentrate your weight on a smaller area than your foot was designed to walk on, increasing pressure and often creating pinch points. They can make balance difficult and sink into soft materials, like sand or turf. Go with low heels or flats as much as possible, especially if you will spend much time on your feet in these shoes. There doesn't seem to be as much space for padding in dress shoes as in athletic shoes, but take all you can get. Any layer of foam or rubber that can cushion the impact between hard pavement and your foot will make standing and walking more comfortable.
Don't purchase shoes that feel too tight, expecting them to stretch to fit. Consider avoiding tall heels, especially high, pointy ones. Look and feel for padding and cushioning.