Here (https://imgur.com/a/39ycE ) are images showing the yellow boxes specified. I was able to remove the text (which were blue) but the boxes do not get deleted after selected and pressing delete. The boxes are also unable to be 'cut' or 'copied'. Preview version is 10.0, Mac is High Sierra Version 10.13.2. Preview is opening a pdf. Nothing shows up in the Annotation bar of Inspector. I have yet to stumble on the yellow boxes in another pdf