How to start a small publishing company

I can't advise you as to Louisiana law. But if by "DBA" you mean a sole proprietorship, that puts you in direct line for liability exposure.

A limited liability company (LLC) or an S corporation is a legal entity from which you can derive many benefits, not the least is liability protection for you and your personal estate.

As to your industry, I can't imagine that any of this would be different for a publishing company. But, as always, be sure to talk with an attorney knowledgeable in Louisiana law.