The issue of "painlessness" / "aponia" is controversial and needs much discussion.
I have collected on this page my current understanding of the issue, as well as cites and references for the position that painlessness is not paradoxical, but is in fact simply understood as a life so full of pleasure that no room is left for the experience of pain, a formulation found stated by Cicero.
This is not the only possible formulation of this issue by any means, but it seems to me that any formulation must be consistent with the full scope of the available evidence and be consistent with the role of Pleasure/Pain in the Canon of Truth, the insistence of Epicurus that words be used in ordinary, familiar, and clear meaning, and the many statements to the effect that "pleasure" is the guide of life.