Trying to copy/paste a graph from Excel to Illustrator (or open a PDF from excel). Sometimes it pastes fine as vector shapes, but other times a complex graph paste as pixelated images(the lines still paste as vector lines though). For example instead of pasting a cluster of circles, it pastes a cluster of pixelated circle shapes with a mask....Why doesn't it just paste as vector circle shapes as usual? Is the graph too complex? What are my options?