I'd second this request.
What the Editor already seems to do at present, it caches ALL pages of the current document(s) AFTER they at least have been shown once.
Thus, after having scrolled through the entire current document ONCE, every subsequent scrolling seems to be even smoother and faster (than the already incredible speed of the Editor).
That is even more the case for the thumbnails pane. Other than its competitors, PDF-XChange Editor also caches all thumbnails AFTER they have been shown at least once in the thumbnail pane.
Simililarly, the unbelievable text search speed of PDF-XChange Editor is "only" reached AFTER the very first text search, which seems to cache all text of the entire file, making every subsequent search almost as fast as the speed of light.
Thus, why not use a few little (unhurried) background threads right after the opening of every PDF, crawling the entire file:
a) for its text (making text search blazing fast from the very beginning),
b) creating and caching all thumbnails of the entire file (enabling speedy thumbnail browsing in long files from the very beginning), and
c) pre-rendering and caching all pages of the entire file, at the current zoom level (enabling smooth and fast scrolling even in heavy files from the very beginning).
Since the Editor does all three things (a, b, and c) anyway later on (when the user scrolls and works his way through the file) this would also not mean that it's a waste of resources or memory.
Rather, it would make the already fastest and smoothest PDF software on the planet even more fast and smooth. PDF-XChange Editor eventually would end up in a league of its own, unassailable.
European Patent Attorney
PDF-XChange Editor Plus