Decal Paper

Sometimes it's more- or less-visible, depending on your printer's inks and the thickness of the decal paper, but it sort of 'goes with the territory.'

The only solution I've found is to touch up the edges with paint. It's much easier to do this before the decal is applied, rather than when it's on the model.

A tip based on hard-learned experience: touch-ups with enamels seem to flake less than with acrylics. And, either way, go easy: too much paint will 'glue' the decal to the paper edge. (Ask me how I know....)

I've found a little Future on the spot I'm putting the decal before I apply it, and then a little future after applying it seems to works wonders. I just spot apply with a q-tip.

I use one of those sharp double ended toothpicks as a very fine paint brush, and run a little bead of the color I used under the decal to fix that edge.  One of the additional little things you have to do when doing light colored decals over a dark finish.  You get used to it.

BTW, there is a decal forum among the finescale forums, down below under the Tools, Techniques and Reference Material section.  Working with inkjet decals has frequent threads in that forum.