The San Francisco 49ers hold 13 choices, 10 of them eligible for trading, in the 2013 NFL draft beginning at 8 p.m. ET.They're in position to trade up, trade down and/or stockpile picks for next season.Matt from Redding, Calif., asked through the NFC West mailbag how the 49ers acquired the additional picks. The chart breaks it down.2013 San Francisco 49ers Draft Choices