As a generic request, paste an image on PDF sheet.For example, my student use PDF reader with annotations capabilities and sometime they've to paste a picture I've drawn on the (real life) whiteboard (one student put the picture on Discord and other ...
Few highlighters colors (predefined). Could be: yellow, green, orange, red, purple and blue (like real "stabilo") with 35% of opacity.That's only example, development team could check for best renderer 珞