It doesn’t matter if you put Ltd or Limited. The former is an abbreviation of the latter so there is no difference between the two. You can only legally put Ltd or Limited if you have formed a Limited Company though. On formation, you will have registered your company name ending Ltd or Limited. Therefore, you may want to use the same to keep things consistent. However, it doesn’t matter from the legal side of things.
If you are registered as a sole trader, then you cannot legally use Limited at the end of your business name.