What and which legal documents needs (for example if any licence) if someone want to open centralized exchanges like Bittrex?
Or there is no need any documents for open exchange? Want to know details.
As far as a I know exchanges are money transmitter, so you have to check with your local government what licenses you need to apply for. However, since this is going to be a lengthy process and could involved big sum of money, the question is, do you have the budget, because if you have then it is quite very easy and you can hire experts to help you out.
Apart from your local government, shouldn't you also check whether you can operate in different countries?
I know the US is very strict about this sort of thing, it could be the case that you should just bar entry for everyone from the US.
Technically, you'd need to get licensing in order for every jurisdiction you operate in. (meaning all countries your customers are from)
As @suzanne5223 says, you can do this through Estonia for the EU, but get legal council before you start, I can't reiterate that enough.