Lay a large sheet of plastic wrap on the counter; sprinkle with half the combine vinegar, garlic, and sage. Place cutlets on plastic wrap; sprinkle with remaining vinegar mixture. Sprinkle lightly with salt and pepper. Cover cutlets with second sheet of plastic wrap. Using kitchen mallet or bottom of heavy pan, pound cutlets to flatten. Let stand 5 minutes.

Sprinkle both sides of cutlets with flour. Heat oil in large skillet over medium-high heat; add half the cutlets and cook until browned on bottom, about 1-1/2 minutes. Turn and cook on second side until cooked through, about 3 minutes. Remove cutlets to oven-proof serving platter; keep warm. Repeat with remaining cutlets.

Heat broth and lemon juice to boiling in skillet; cook until reduced by half. Pour mixture over cutlets; serve immediately.