I also got the same behavior you described in your first post.
The PDF file blocking import is the LibreCAD user manual. I also tried to rewrote it using pdftk:
Code:
pdftk manual.pdf cat output manual-new.pdf
but did not solve the problem.
I'll try me too to install Nickel Menu (I used it in the past, but I uninstalled it).
I think it allows to extend the timeout when loading a particular "heavy" PDF (i.e. with big images), even though my PDF is not so "heavy"...