You can do a M1 increase between the two edge stitches. I usually just knit the edge stitch, but if you feel your edge is too loose, you can slip it if you want. Slip as if to purl so you don't twist the stitch. I don't think knitting the last stitch is necessary for a sleeve edge--it creates a more decorative edge for a scarf, but it might not be the best for seaming.
"Trust the pattern!"
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IngridKH on Ravelry