One of the clips in the project I'm working on was recorded at a very low volume, and I want to simply duplicate the audio track, to effectively double the audio output (I've already maxed out the gain). I tried selecting the track, copying it and pasting, but it just pastes to the same track, not to the new ones I've selected. 

I suppose I could just copy it to a blank space on the timeline and then move it to the new track, but it seems there should be an easier way. Any suggestions?

Tools > Audiosuite  has a Gain that can add another 96dB. 

For copy and paste of tracks to different tracks:

Use cmd+ option+c, which loads the copied material into the source monitor. Then drag the source monitor contents to your new audio tracks, or patch your tracks and overwrite onto them. 

Great! Thanks, that did it!