Pardons are often granted before someone is found guilty. The most famous pardon in US history, Ford's pardon of Nixon, was before he was formally charged with anything. The blanket pardon of Vietnam draft dodgers also wound up pardoning many people who had not yet been charged. A pardon of Snowden would
not be improper procedure.
His accepting the pardon would be an admission that he performed the actions in question, but he admits that anyway.
