Every time I try to view a pdf file on Firefox I can view the file but in the lower right 1/4 of the screen I get a graphic of a page with shaded areas representing lines with writing on them. There is a type of pen cursor moving along the line. This happens with different pdfs - from the internet and from my saved files. This doesn't happen on another computer with Firefox. I've deleted and redownloaded Firefox an number of times, also tried troubleshoot mode - no improvement. Virus scanned, restarted a number of times. Pdfs work on edge and chrome and reader with no problem. I have a screenshot. Any Ideas? Thanks