There are many duplicated image objects(/subtype /image).
Can anyone help take a look?
Introduced into the 1.9.x development series was the notion of copy-on-write snapshots which the PDF uses to eliminate duplicate image patterns, i.e. it should only emit an image once. Please try the 1.9.4 snapshot, though it still has a number of known regressions in the PDF backend, to see if the behaviour improves.
Chris Wilson, it is great to know this things. Thanks a lot