Removing Scratches from Clear Plexiglass?

Getting scratches out of plexiglass is a real problem. I can think of two ways that can help make the scratches appear to disappear.

1) If it is large area with a lot of little scratches you could use # 800 or #1000 wet/or/dry sandpaper and make the whole surface evenly sanded.

Yes, you are going to make it worse but read on. Then wash it off with dish soap and water and rinse well and air dry. Then spray that surface with clear enamel spray paint. How good this will turn out depends on how good you are with spray painting properly.

Nice even coats will look amazing. Sloppy work will show dripping, ripples, dirt sticking to the paint.

This is a trick I use to make my old cars plastic headlight cover to look new again when they start turning milky white from the sunshine.
The other trick is buy a bottle of glasses scratch remover and try that. Again this depends on your application skills and severity of the scratches
I hope this helps.