We have a runner in a heavily trafficked area over our engineered birch floorsninstalled less than 3 years ago. We rolled it up to showcase the floors when we put it on the market. When we did, a strange pattern, almost like halftinenprinting dots, is showing up on the floor and can't be removed. We tried our usual floor cleaners - pledge, Bona, etc., even tried rubbing an area with denatured alcohol - but the "image is still there. It's not adhesive or anything with texture. Just a lighter pattern that seems to be part of the finish now. Has anyone run into this? What can we do?

https://www.flickr.com/photos/61278483@ ... datetaken/

The pad will affect the way the finish wears. This must be where the pad touches the floor. It can be like a scratch and will sometimes polish off getting shinier with stocking feet traffic.
Sometimes a plasticizer in the pad or carpet backing will "soak" into the finish so the shape of the rug is another color compared to not being covered. The plasticizer will gradually disappear after a couple of months when the rug is removed.