I was going trough a 30 page pdf for making it accesible for the screen reader. The document had multiple layers per page (for example boxes and text overlay over photos) and when adding the reading order, it changed also the the order of the layers, causing that photo was over the text. If there's only a photo and a text "bring forward and bring backwards" or copying and pasteing the text again works, but for example I had a page with multiple different elements that caused lot of clicking elements backwards and forward to have elements shown and in right reading order fo accessibility.