There is no information indicating if Voltaire was either right or left handed, but in one of his pictures he is seen holding a quill with his right hand. He was born on November 21st 1694 in Paris, France and died on May 30th 1778 in Paris, France. You can find out more details on http://en.wikipedia.org/wiki/Voltaire.
This is purely observational... but in his statues, he is holding his quill in his right hand. This would lead me to believe right-handed... but I am unable to confirm this through any on-line sources.