In my experience, you cannot be a successful copywriter (one who writes content to acheive a sale or to induce a desired call to action) without marketing skills.
There is an abundance of people who can write, but it takes marketing knowledge and an astute psychological understanding of consumers to produce content that is engaging and enticing for a particular target market.
In order to truly speak to a particular company's clientele, you must perform the necessary market research. Find out what makes this target market really tick. Then, and only then, should you formulate the words to accomplish the particular objectives at hand.