It is your property. The artist is transferring copyright to you. You have the right to do anything you want with it.
This is the nature of commercial art. Commercial Art and Fine Art diverge primarily in two areas:
1.) Fine Art is the vision of the artist and is sacrosanct.
2.) Commercial Art is the vision of the client and can be adjusted ad infinitum by multiple artists.
Both require great skill. Both are often commissioned work by corporations, municipalities and governments. Both have a place in museums (because, after all, most of the artists who worked during the Renaissance were commercial artists. Last time I checked, Michelangelo didn't even want to paint the Sistine Chapel and the commission was forced upon him! Tell me that's not a commercial art assignment!)
If you hire a graphic designer the work they create belongs to you. Hopefully, you have enough skill and vision that you can recognize strong choices, isolate weak ones and have them redraft only the weaker parts of their design.
This is a tough gig for both the client and the designer. I empathize for both parties. I've been on both sides of the fence.
As a designer, one often gets clients who don't know what they want, ruin the best parts of a design because they don't understand typography, layout, color theory or the history of styles and want arbitrary changes because "they want to see what's possible" which is a bit like telling an interior decorator "I want the couch on that wall. No, that wall. NO, that wall! Oh, I just want to see what is possible!"
As a business owner, one often gets vendors (and that is what the designer is, a vendor) who have egos, who have overstated their skills, who are resistant to redrafting because they've fallen in love with their own work and have forgotten this is commercial art, who take on too many jobs and can't dedicate enough time to you, who are emotionally unbalanced and they've become a freelancer because they have issues with authority.
It sucks for both sides. Hiring a mechanic, bookkeeper, accountant, carpenter, janitor and security for your company is far easier than hiring a graphic designer. Finding a client who isn't going to sabotage the graphic design process is equally hard. I'd guess that less than 10% of client/vendor relationships in this field are healthy ones...and, the healthier ones usually come from both parties getting older, having lived through multiple nightmarish experiences and slowly realizing how valuable the other party is.
But, I digress. :)
It's your property. Do what you want with it. And, don't apologize or feel bad about it. You paid for it. Just, make sure the changes you're making make sense. Unless you've studied this stuff for years, gut instinct isn't the way to go. Like my aunt told me years ago "Everyone thinks they have taste. But, since taste is rare, most people are terribly self-deluded". So goes the battle between clients and vendors regarding graphic design. And, that's also why I pay more for designs. I'm paying for style. I don't want a hack. I want someone who has incredible style.