There is no such as legal documents for a coin. Perhaps some Exchanges have licence documents which is not much useful for traders. More important is how trustworthy an exchange. Only you may read on whitepaper about a coin, their future development plan and what is concept. As we can see most of project last year's are not successful even after listed on exchange. There were some sudden pump and dump again. For general traders like us, better to avoid dealing with new coin after listed on exchange. Just wait few months and look on the movement. Likely you would get more better chance to get profit from it. If not, then just skip, at least you had not lost anything.