Thanks for the info, Quincy. I'm sure you can hear the amatuer knowledge in my initial post. Thanks for being helpful. I thought there was some sort of form I had to file in order to classify my partnership or business into another industry. As if to say, I didn't think I could wake up one morning and start publishing books/sponsoring signed authors to write books which they've shared rights to. My partner is extremely silent - doesn't ask about anything and has empowered me to make all decisions so there aren't any objections on his end. Am I correct in concluding that no such "form" exists, based on what you've shared with me?
I just have to do well enough in that industry to remain in business?
You will not only benefit from sitting down with a business professional in your area, this appears to be a necessary action for you to take.
You will need a personal review of your current business structure (limited partnership? general partnership? limited liability partnership?). You will need to have an agreement with your partner to change businesses and divest yourself of any assets your clothing business might have. You need to investigate what sort of licenses or permits you will need to operate your publishing business out of California.
Most importantly, perhaps, you will also want to become knowledgeable about the publishing business. For example, you will need to have agreements drafted and signed by each of the authors that will transfer or license their rights in the works to you, to allow you the legal right to copy, publish and distribute the works. Without these licenses/transfer agreements, you would be infringing on their copyrights. The publishing contracts will need to detail exactly what you will do in exchange for what price. Any and all problems that might arise in the publishing of a work should be clearly addressed in the signed contract so if a dispute arises later, the contract spells out how it is to be handled.
And, as latigo implied with his post, a partnership might not be the smartest business structure for you. Also as latigo said, instead of "repurposing" your current business, it is probably best for you to dissolve your current business and partnership and start all over.
But because starting a new business, especially one as complex as the publishing business, is more complicated than simply changing the name of your current business and saying you are now in the publishing business, you will need a professional's personal assistance. There are far too many legal, tax and financial aspects involved to provide you with effective guidance on a forum.
Good luck.