Leo's double is a timely boost for Norway, whose World Cup qualifying campaign has been severely damaged by recent defeats while the experienced midfielder was unavailable through injury.
Leo struck in the 74th and 75th minute after Hristov had shot Bulgaria into a first minute lead.
Gary Doherty won the Man of the Match award as the Republic of Ireland went to the top of World Cup qualifying group 1 with a 3-1 win over group minnows Andorra in Dublin.
Doherty failed to register his first international goal, but received great credit for providing two goal assists. His cushioned header in the 34th minute set up Kevin Kilbane to score Ireland's equaliser after Lima handed Andorra a shock lead two minutes earlier.
Two minutes later Doherty was in the thick of the action again and Mark Kinsella profited from the rebound after Gary planted a header against the bar. Gary Breen completed the scoring in the 76th minute.
Neil Sullivan turned out for an inexperienced Scotland team on Wednesday evening as they emerged from a tough trek to Poland with a creditable 1-1 draw.
Oyvind Leonhardsen grabbed two goal in two minutes as Norway came from behind to beat Bulgaria in a friendly on Wednesday.