You can change the gain of audio regions with the Gain tool, or in the region or cell inspector.
Get started arranging regions in Logic Pro for Mac - Apple Support
Import compressed audio files into Logic Pro for Mac - Apple Support
General project settings in Logic Pro for Mac - Apple Support (GW)
Use the tempo fader in Logic Pro for Mac - Apple Support (MN)
Overview of the Logic Pro for Mac Audio File Editor interface - Apple Support
Common parameters in the Logic Pro for Mac Environment - Apple Support (KG)
Apple Logic Pro Review
Use Logic 10.7.5's New Region Gain Tool - iCreate
Resize and reorder global tracks in Logic Pro for Mac - Apple Support
help.apple.com/assets/6463F7B2A10C47224C458830/646
Logic Pro X: Six Tips & Tricks
General Audio settings in Logic Pro for Mac - Apple Support
