If I pay someone else to write original content, an article, for our website is it OK legally to submit those articles to article directories ? can they be submitted to directories with our name or must it be the author whom we paid..? either case, we will use our website links somewhere within the articles or at the end since we are the owner.
Yes that's fine to submit them in your name to article directories. As long as you have an agreement. It's common.
The copyright rests with the person who writes the articles unless you have an agreement beforehand. It's always sensible to have something on paper confirming that when the article is written you gain the intellectual rights to it.
There are various kinds of rights with respect to content of a person. If you have an agreement that you have full rights to the content, can modify, edit it as per your discretion and can claim the article as your own, I see no reason why you can't submit it to article directories. I am no legal eagle btw .