1. There is no need to pardon because he hasn't been convicted of anything.
2. As a private contractor, he is protected under the Whistleblower Protection Act. That act does not exclude whistleblowing on federal agencies.
3. He probably could have done it a better way, such as going to a liberty oriented Congressman.
4. Much of what he said isn't news. Programs like Echelon have been known for decades. It is just a matter of exposing to the public how extensive it is. Its big impact, which is a positive thing, is making people aware of how important privacy issues are.
5. Some like to compare Snowden and Manning. They are very different circumstances. Manning was a uniformed soldier who 'leaked' actionable intelligence. That isn't whistleblowing. There is a certain chain of command and process for addressing what you feel is illegalities or problems in the military. He directly violated his oath and in any other time, he would probably be hung for treason. Snowden was a private citizen contractor and what he 'leaked' was not actionable intelligence.