Talk about multitasking. As part of a whirlwind, 45-plus city promotional tour for National Parks, Ken Burns threw out the first pitch at the Florida Marlins’ game yesterday. He also used the opportunity to pitch something else: His upcoming baseball doc. “We just started editing what we’re calling The Tenth Inning,” he told The Palm Beach Post of the project, tentatively set to air on PBS in September 2010. “There’s so much that’s gone on and we’re going to really tell the story, good and bad. There’s been enough water under the baseball bridge since 1992, (which) was the last action we described.” Much more on the massive outreach for National Parks: America’s Best Idea in the May 11 Current.