Speculating, but I wonder if this is because Evince currently renders completely new text on a solid background over the top of the document, rather than highlighting the text that was already drawn in the document; eg. the highlight does not exactly match the shape/size of the original document text and neither can the original text be seen underneath when the highlight is active.
Speculating, but I wonder if this is because Evince currently renders completely new text on a solid background over the top of the document, rather than highlighting the text that was already drawn in the document; eg. the highlight does not exactly match the shape/size of the original document text and neither can the original text be seen underneath when the highlight is active.