The 22-year-old joined the Whites following his release from league rivals Maidstone United in November 2015.
He made his debut for boss Chris Kinnear’s side as a second half substitute in the 4-0 win against Gateshead at Crabble in February 2016.
Pinnock made twenty-three league appearances last season and also came on as substitute in the Emirates FA Cup Second Round defeat against League Two Cambridge United at Crabble.