In any case, for safe trading, you need to undergo verification on the exchange. Another question is that technical support for Bittrex works gently not so well and if your documents were not automatically received, you will have to wait a long time for them to be processed manually.
it's all not about safety or something like that but instead it's a specification,
for you who is living in europe or certain area and did not live at their so called 'restricted area',you do not need to worry because they will not do nothing to you and your account absolutely.
but for them who want to verify their account and live outside from that places i am afraid there'll be a lot of problem that will happen.
for example :
whenever you send your verification they will not answer your ticket immediately until you're sending a back up ticket.
plus when you have a balance in your account,you can not withdraw it immediately or i called it 'hostages'.
so in conclusion everything is messed up and i do not recommend you guys to trade it in there at this moment.