On Saturday 17 January 2015, Dan Youngquist wrote:
> ... 
> > 2. It "forgets" a page as soon as it's no longer displayed, and has to
> > re-render it to display it again.  It's as though Memory Usage is set to
> > Low instead of Normal or Aggressive, but the setting makes no difference.
> >  This is very inconvenient in cases where it takes more than a fraction
> > of a second to render a page, which is the case with most of the PDFs I
> > use.


I can verify that the default behavior is to redraw pages on scroll, but not 
some of the other details for R14.0 on Wheezy.  Changing to "Aggressive" 
memory usage speeds up page display and thumbnails are remembered.  It's 
still possible to see a X page flash if you scroll very quickly but the 
overall speed in the default and aggressive setting is good.  It's about as 
fast or faster than Okular.  This is with a 2008 Thinkpad x61s.  

For fun, I fired up an Etch VM.  A small pdf rendered instantly, but a larger 
one had the Xs, but was still speedy.  That's basically what I remembered.