🚀 go-pugleaf

Audition can do nothing to incoming audio - it just takes what the soundcard passes to it and writes it to the disk. So to raise the level at the outset, you need to do so with any external mixer you might be using, or with the windows mixer or soundcard mixer (though in the case of most pro soundcards, recording level is fixed anyway).

You might wish to consider installing a compressor (physical piece of equipment) between the external mixer - if any - and the PC, to even out the levels before they get to the PC. Otherwise, you'll need to process the file afterwards, which I realise you may not have time to do. (Though with a reasonably specified PC it shouldn't take more than a few minutes even on a long file - instead of spending money on external gear, perhaps a PC upgrade might be better value? What are you using at present?)