I was first author of a paper that got accepted to a top-level conference after all the admissions deadlines. When I got the notice of acceptance I attempted to update all of my applications. I was able to simply modify many of the the applications myself. For the others, I sent an email to graduate admissions. They all gave auto-replies, one human reply that said they couldn't update it, and one that said they would update it. So for me, it was definitely worth it to contact the admissions department.
Different schools have different policies about this. If they explicitly say no updates whatsoever can be made, don't bother them. If not, why not try? You would be paranoid to think that such a thing could lower your chances of acceptance. In reality, it will just be an administrative assistant who addresses your email and makes the update, and the admissions committee may or may not notice the change.
On the other hand, failing to list something on your resume is less understandable, since you could have prevented this problem. I think they would be less likely to want to help you because you were forgetful when writing your application. You might have to pick your battles and try to update the publications list and not the resume.