The entire concept of copyright is that it is easier and cheaper to duplicate a work than it is to come up with the work in the first place, and thus to encourage innovation, the original innovator's investment is protected from mass production of their works wherein they are not compensated. Buying and editing a work, where the originator is compensated for their product, and the editor compensated for their work, is entirely in keeping with the concept of copyright.
No because part of what copyright is about is protecting the content as well, copyright holders get to decide what modification are made prior to distribution, if they are no longer allowed to do that then they've lost half of why copyright exists, and with that half gone it won't be long before they start losing the money (hey why should you pay somebody for a product that you modified before distributing, it's just as much your product as theirs at that point).