Does changing the RAW file introduce noise?

When you use lightroom or some other program, does every tweak introduce noise or is that not affected when you post process?

A Raw processor shouldn't introduce noise but it may make the existing noise more visible in a couple ways -- first, if you brighten dark areas, noise that is there (as it is in any image) can become increasingly visible. That's just a fact of life. Then, if you have visible noise, it can become more "gritty" by sharpening. That's another fact of life.

But you can find a balance between sharpening and noise reduction to get the best results. And, Lightroom has brushes that you can use to selectively sharpen an image (or soften the sharpening) which can come in handy.