What happens if you knit with smaller needles?
The real way to change the number of stitches that you knit in an inch is to change the needles that you’re using. A needle with a smaller diameter means that you make smaller loops when you wrap the yarn, and therefore you get smaller stitches. Likewise, bigger needles make bigger stitches.
How do you convert a pullover pattern to a cardigan?
If your pattern was intended to be a cardigan, all you have to do is eliminate the steek stitches and replace them with a selvage stitch at each edge (the first and last stitch that you will attach the front band to).