The team announced the deals Wednesday, adding depth on their young roster that features No. 1 overall pick Cade Cunningham.
Detroit acquired Joseph after sending guard Delon Wright to Sacramento in March and he averaged 12 points in 19 games for them last season. Joseph has averaged seven points a game over 10 seasons with San Antonio, Indiana, Toronto, the Kings and Pistons.
Jackson averaged a career-high 9.8 points over 40 games with the Pistons. He has scored nearly eight points a game over three seasons with New Orleans and Detroit.
McGruder averaged 5.7 points in 16 games last season in Detroit. He has scored almost six points a game over five seasons with Miami, the Los Angeles Clippers and Pistons.
The Pistons need all the help they can get after winning just 20 games each of the past two seasons and failing to have a winning record for five straight years.