Need to Raise the levels from -18db to around -6db before I get it mastered.

Why not let the mastering engineer do it?

Aside from getting the ME to do it, do you not know how to turn up the level of a track?... It's in page 1 of the instruction manual... 

Use the normalize function BUT..... set the maximum level to less than 100%. Something like 90% to 94% should leave enough headroom. 
 
Or...like was mentioned, if you are having it professionally mastered, they can handle that quite nicely.

i read the title as "Need to Raise the levels from -18db to around -6db before I get arrested"
 
carry on, as you were

Remix it hotter?  Actually, Jim's answer is the easiest if you are happy w/ the mix.  But leave room for the ME - raising levels is part of the job description.
 
@

Why???
 
Or rather, to what level are you referring, peaks, rms, average??? And of course what style of music?
 
I kinda like the openness of 18 dB of room for peaks - in fact musical peaks can exceed 18 dB! And you aren't losing a lot of bits by providing some breathing room...

fitzj
I have a stereo track that I recorded from a console which is around -18db. I need to get it up to around -6db before I send it for mastering. I tried a gain envelope and then used a compressor. It seems to make the track a bit  harsh. 
What is the best way to do this?

Harsh is a big word, define harsh. I have used a comp without compression as a gain booster, and I've used expanders, with and without expansion as gain boosters, EQs, with and without equalization, and, believe it or not, gain plugs. Hi freq reverb adjustment. Reverb foldback levels. Gain knobs on pre's, power amps, powered speakers, faders, boost buttons and even hearing aids.
 
Ok, NOT hearing aids.
Yet.
 
Why am I typing all this?
 
Cuz in the time it takes you to read it, you could have defined "harsh" and thougth up ten different gain strategies to negate some or all of the negative benefits of "harsh" and be well on your way to implementing and comparing them.
 
I am not giving you any grief at all, because asking a wide audience for both standard practices and suggestions is an excellent move, BUT...
 
You are going to audition some or all of the suggestions given and judge the results, so you might as well be working on your own ideas to see ...a lot of different things....like how well you can anticipate industry standard answers, how innovative you are, who here gives advice that works for your ears, and how well your equipment and software options fit into the bellcurve.
 
For every action, there is an equal and opposite reaction. The more actions you can pop out of your pocket and predict the outcome of, the more you have mastered your world, and the more likely you are to spend your time breaking gound no one else has tread before.

Good call letting the ME do it. But I thought it should be pointed out that no simple gain operation will alter the dynamic range. The hotter signal may sound compressed, but that's just a psycho-acoustic effect or possibly a function of your monitoring system or room acoustics.
 
Also, just incidentally, if you wanted to normalize to -6dB, you should use 50%.