Do pros touch up their photos?
I would have a hard time agreeing with anyone who claimed that photos pros publish were left completely as shot in the camera. From the days of film and slide photography and darkrooms, photographers have always done certain things to every photo. First of all cropping is one of the simplest and most important ways to change any photo, and I can't imagine any photographer claiming that cropping was not a helpful part of the composition and creative process. The second thing that photographers did decades ago in the darkroom was to control exposure when making prints. If I understand correctly, there is no way to make prints from a negative without explicitly deciding what the exposure of the print should be based on how long each print sits in the chemicals. So along those lines it doesn't make sense to get the digital photo off a digital camera and not make small changes to the white balance, exposure, white point, black point or levels.
Pros often do extensive dodging and burning or other kinds of modifications using software like Photoshop. Most magazines are heavily doctored and may include removing blemishes, wrinkles, etc.
In my own photography I rarely let any photo go by without at least changing the white point, black point, white balance, or exposure, and cropping to improve the composition of the photo, or removing distracting elements at the edges of the photo. In addition, in order to bring a level of consistency to a set of photos I try to do white balance and exposure to make all the photos go together. For the most part since we take so many photos we don't have time to do a lot of manipulation, for example HDR, or heavy Photoshop touching up with the patch tool. In that sense we mostly let the photos stand on their own.
In terms of your own photos, an important part of the process is to understand the limitations of your camera, and to account for them as you take your photos in the field. This includes things such as cropping and later exposure adjustments. For example it is common for digital cameras to overexpose photos, so I compensate for this by purposely underexposing them slightly when I take the photo. Then later I increase the exposure and this avoids artifacts, for example turning the sky from beautiful blue to an ugly, clipped white color. I'm thinking about these things when I take each photo.
If you take a lot of photos, and someone goes through them and changes them to a degree that you're not comfortable with, then perhaps you should have a talk with that person. People's aesthetics will definitely disagree and this is an interpersonal issue, but there is a sense that the photo you take should ultimately, hopefully reflect your vision of when you took that photo.
At the same time, there is much to learn about being open to small improvements that have a dramatic effect on the quality of your photographic output. In the same sense one of the most important parts of photography is the selection process. Going through photos after a photo shoot and removing all but the very best photos is one of the easiest ways to improve your photographic output.
Finally, what should people do with their own photos, in terms of touching up? I have strong opinions about this, and I personally feel more comfortable with an aesthetic that lets the subject of the photo, and the composition, do the talking. I don't have a lot of patience for heavily doctored or gimmicky photo manipulation. In that vein, I have sought to make only the smallest changes to my own photos, and make it seem like they were not changed at all. I want the viewer to have no distraction when they see the photos. I want them to think that they could've taken this photo, themselves, "I wish I had taken that, I want to go there! I want to see that!"
I think there is value in understanding what manipulations are available in various software packages. I think understanding some of the more advanced techniques of achieving different looks can help you understand the limitations of your own equipment, but I think personally in the photos that I share, I want people to feel that they are genuine and straightforward.
Finally, one of the most subtle and surprising things about photography is the fact that every camera has opinions, and has limitations, and is unrealistic, so to speak. A simple example of this is that different camera manufacturers have different "looks." There is simply no way for the technology in the camera to accurately reflect what you see when you take the photo. Engineers have made thousands of decisions about what to do in different scenarios and how to manipulate the image when it writes it to the card on your camera.
Historically, in photography, black-and-white photography allowed a lot more leeway for the photographer to manipulate the image without the viewer feeling that it was unrealistic or wasn't accurate, since the image already had no color, which is already unnatural, and the viewer has already suspended disbelief and agreed to accept the photo as a piece of art meant to express an aspect of reality, and not reality itself.
The problem with color photography is that it works well enough for us to forget that the camera is just as limited and there are just as many if not more aesthetic choices about how to render the final image as in black-and-white photography. But we are still just as concerned with the verisimilitude of the images from the camera, and we may be unwilling to modify what the camera decides, thinking there's something somehow sacrosanct about it. Nothing could be more wrong, since the engineers have made many arbitrary decisions for you and there is no Platonic image to taint; it comes pre-tainted. This leaves the decision of how to render the final image as a matter of aesthetic or artistic or creative vision. And actually peoples' opinions and approaches and experience will change how they approach each image.
Maybe one day when the display technology is advanced enough in terms of dynamic range and color gamut, we will be able to trust the images from our cameras and consider them realistic and perhaps at that point it would be worth arguing that images shouldn't be manipulated. But the reality is current technology is limited enough that we must make decisions and we must disagree with what the camera does, at least some of the time.