The same issue is raised earlier with post 12938. though it still not get resolved with viewer v3.4
so raising again with groupdocs.
In earlier version of 3.x, preloadPagesCount was not working. We can see its working better now in v3.3 but when we are loading large files (~2 MB or more). Its loading first page quickly but its taking too much time load other pages. We have set preloadPagesCount = 1. I have attached one sample PDF with this conversion (general_relativity.zip), could you please investigate on this issue and provide your comments.
We have also observed Thumbnail is taking too much time to load. Please look into this issue also.
Please acknowledge once you able to grasp the concern raised.