yes, this happens to me as well and I have a pretty normal and common full HD laptop screen. I noticed that the number of pages shown is the actual number of pages, but the counting along the scrolling doesn't work well. like it increases the page number after one and a third of next page or so, so when you reach the last page, the number is lower than the actual number on the page.
thanks, but is there an opera plugin for this? I have found only a version which opens documents saved in PC.
I actually haven't find any related settings in opera, where to change viewer or something like that, am I missing something?