Taylor, a running back, ran for a career-best 1,530 yards as a senior at Stanford. He also caught 41 passes for 287 yards.
Swope, a receiver, comes to Arizona from Texas A&M, where he caught 252 passes for 3,117 yards and 24 touchdowns in his career. He ran a 4.34 4-yard dash at the NFL Combine, but slipped due to concerns over a history of concussions.
Ellington was a consensus All-ACC first-team selection last season after picking up 1,081 yards and eight touchdowns.
Jefferson, a tight end, began his career at Rutgers as a quarterback but finished it by posting a career-best 20 receptions for 168 yards and one touchdown as a senior.
Still unsigned are first-round pick Jonathan Cooper, second-round pick Kevin Minter, third-round pick Tyrann Mathieu and fourth-round picks Alex Okafor and Earl Watford.