Unpasteurized juices are safe if they are kept cool and consumed within 3 to 4 days after the juice is extracted. After this time bacterial pathogens become present. The FDA recommends thermal processes to achieve a 5-log reduction for oocysts of Cryptosporidium parvum.
However, just like milk, if the juice is consumed fresh there is a very minute hazard.That said, the problem with pasteurized juice is the loss of nutrients. So I am going to answer with "fresh is best" and pasteurized is a good, safe alternative.
"Cold pressing, on the other hand, extracts juice by first crushing the fruits and vegetables, and then pressing them to squeeze out the highest juice yield, all without using heat. This produces a drink that's thicker and has about three to five times more nutrients than normal juice". - Source http://www.shape.com/blogs/fit-foodies/are-green-j...
Today there is a new school of thought which suggests fruit juices should not be consumed in quantity. The claim states that the human digestive system is not designed to break down the sugars at such a fast rate, but rather designed for 1 to 4 portions of whole fruit. If fruit juice is to be consumed it should be done so with small, infrequent sips. Sugar is sugar, fruit or not, and consumption should be at a minimum.