The problem is PDF and the viewers. some/most expand ALL the
compressed images and create thumbs from the images before they start
display, This uses huge amounts of memory, a technology fail, they
just dont fit certain work.
"If" you are lucky the viewer keeps it compressed so it fits in memory
and only uncompresses a single image that is being displayed, this
stops niceties like thumbs unless a background thread goes through the
images and caches the thumbs (slow), this is where even a tiled tiff
viewer could be a lot better.

Someone needs to do a tiled compressed format along with a viewer and
banish PDF to the other side of the moon.

Dave Caroline