images not smooth in pdf

I've seen similar questions - but the asker was not able to provide enough details, and I am hoping to get to the bottom of this. So here is an image I made in illustrator

I embedded it into an inDesign document(where it looked fine) - then exported it using the "high quality print" preset

it has been scaled down(shrunk) - so to me that should mean that it would be even less chance of being so ragged. I wondered if it was somehow my screen - but i have a retina display with high-resolution settings. To make sure that wasn't the case I sent it to my second computer (much lower res pc) and here is how it looks there -

even worse!

Image was created using two circles & pathfinder tool + number 1 in a text box