For me, these two are entirely different social media platforms. LinkedIn specializes in promoting an individual's career, or an entire business portfolio which results in secondly, advertising products of that company. Now, Pinterest is more of like Instagram, wherein it features products, services or personal articles to gain traffic that links to their blogs.
These two could be useful for your business but it really depends on what type of thing you do. If, for example, you are a business owner of a store that sells equipment related to engineering or other specialty product that not all common people need, then I suggest you use linkedIn since you'll be able to narrow down your target market on advertising your products there. But, if you are a seller of a product that is suited for everyday use, then you can do more with using Pinterest.