App freezes when reading PDF books with lots of pictures

Also where can i find the iOS version?

Simply substitute the native library.

The iOS version shall be distribute soon.

Note about your file: it's really optimized for print with many postscript filters applied to images.
In some pages there are tenths of images overlaid with transparencies and postscript: for that reason performances was poor.
I'm attaching you a file from Adobe, even if not recent it's applicable.