Here’s a quick video tutorial on adding a stroke to a raster object in Adobe Illustrator.
It’s not very intuitive so it’s unlikely you would just stumble onto the answer. It eluded me for years until I finally decided to hunt down the method. Adobe really should just fix this, already.
There’s no reason in this day and age that we shouldn’t be able to just add a stroke to a raster object the same as a vector object in Illustrator.
Even if it’s not technically the same, to the user it doesn’t matter. Adobe, make it happen! Ok, enough complaining, here’s the vid: