Prior to playing professionally, he attended Western High School in Davie and then Indian River State College before being drafted by the St. Louis Cardinals in the 47th round of the 2006 Major League Baseball Draft. He began his professional career the next year. He posted ERAs of 3.41, 2.23 and 3.11 in his first three seasons. Notably, in 2008, he was 9-5 with a 2.50 ERA for the Quad Cities River Bandits and 2-0 with a 0.50 ERA for the Palm Beach Cardinals. He was 9-6 with a 4.43 record for the Springfield Cardinals in 2010 and in 2011, he was 8-9 between Springfield and the Memphis Redbirds. He pitched for the GCL Cardinals and Memphis in 2012 and in 2013, he was 9-7 with a 4.10 ERA for Memphis. On November 4, 2013, Additon elected free agency.
On November 16, 2013, Additon signed a minor league deal with the Baltimore Orioles. He played 2014 with the AA Bowie Baysox and the AAA Norfolk Tides. Additon became a free agent after the season.
On November 25, 2014, Additon signed a minor league deal with the Milwaukee Brewers. He was assigned to the AAA Colorado Springs Sky Sox. The Brewers released Additon on August 2, 2015.
Second Stint with Baltimore Orioles
On August 9, 2015, Additon returned to the Orioles and was assigned to Bowie. Additon played for Norfolk before he was released on August 3, 2016.
Chinatrust Brothers
Additon signed with the Chinatrust Brothers of the Chinese Professional Baseball League shortly after his release from Baltimore. He also began the 2017 season with Chinatrust before being released partway into the season.
Lotte Giants
He joined the Lotte Giants for 2017. At the time of his signing with the Korean club, he had spent part or all of six seasons at Triple-A, going 28-41 with a 4.41 ERA in 559.2 innings.
On August 6, 2017, Additon signed a minor league deal with the Colorado Rockies and was assigned to the AA Hartford Yard Goats. He elected free agency on November 7, 2017.
Second Stint with Chinatrust
On January 17, 2018, Additon signed with the Chinatrust Brothers of the Chinese Professional Baseball League. On June 9, 2018, Additon threw a no-hitter against the Uni-President Lions, becoming the eighth player in the 29-year history of the CPBL to accomplish such a feat. In December 2018, Additon re-signed with the Brothers for the 2019 season. However, following a start on July 9, 2019, in which he injured his shoulder, he was released by the Brothers the next day.
