If it’s made for laser cutting, it should already be a vector file – no need to trace. You should be able to just load it straight into the Glowforge dashboard to cut.
If it’s PDF, that’s all you need to do. If it’s SVG, you need to make sure it comes in at the dimensions the creator designed it to be. Hopefully there will be something in the pattern or description to clue you in to the proper size; otherwise you’ll need to figure it out from the slot sizes, since those will tell you how thick it expects your material to be.
Here’s a thread with some helpful information about slot sizes: Is there such thing as a slot-width conversion program anywhere? - #13 by geek2nurse