Copywriting for Sales Letter

I need to "tune up" my existing sales letter. I am hoping to make it more effective and impactful, so if that means making it leaner and more "to the point", or making it seem "more personal", I'm open to your professional recommendations. My current letter is a 2-sided letter, in both English and Spanish. Looking for two experts, one to handle the English version, and the other for the Spanish translation.