The 32-year-old Bedard was 5-9 with 3.62 ERA in 24 starts for Seattle and Boston last season after missing 2010 because of shoulder problems.
McLouth spent four-plus seasons with the Pirates before being traded to Atlanta in 2009. The 30-year-old struggled with the Braves, hitting .198 in 2010 and .228 in 2011.
Bedard could step in immediately at the top of Pittsburgh's rotation while McLouth could provide depth in a crowded outfield.
The Pirates had earlier Wednesday signed free agent catcher Jose Morales to a minor league deal.
The switch-hitter hit .267 for Colorado last season before breaking his right thumb June 15 and not playing again.
(Copyright 2011 by The Associated Press. All Rights Reserved.)