Putting a Google translate dropdown on Website sidebar

I have been looking for a way to accommodate other languages without duplicating content in different language translations.

I believe that it is bad for SEO if you have a sub-domain with a direct translation of the same exact content on main page. the subdomain page could also out rank your main language page.

I did find a WordPress plugin that allows you to put a drop-down in the side bar, and you can choose the language you want to see. Does this have any negative effect on SEO search engine rankings?