I bought some Knit Picks lace weight varigated yarn because I LOVE the colors in it. Now, I don’t like the weight. I want to use it as an edging to a DK weight yarn item. If I double it, will it still look good? If I double it, will the weight be enough to look good together? Should I just scrap it and return it? I can’t make up my mind. Perhaps I’ll just keep staring at it for a few days…
Can’t help you with your question, but if you love the color, don’t return it, make a scarf from it, or if you have enough, a simple shawl. Returning yarn just isn’t right. 
Doubling lace weight makes about fingering weight, not DK. It may work as an edging, you’d have to try it to see how it knits up.
That’s probably still too thin. I can give it a try. The majority of this is going to have to go back then because I can’t keep it all if it’s not really all that I wanted anyway. Some of the colors are a little off but two are perfect.
If you knit socks, you can use the yarn for that (doubling it I mean). I recently did that to some lace weight knitpicks wool and it worked great. I actually may just start doing this for all my socks, because I too love knitpicks lace weight colors (Gossamer).