I succeded in getting working my Canon LBP6000 on XUbuntu 14.04. (Following the instructions in this answer). Now the printer works almost fine.
My problem is that PDF files are printed as black pages. More precisely, the output is a black rectangle sormounted by some fuzzy lines.
It happens independently of the PDF reader I try to use (built-in Chromium reader or Evince). I tried printing PDF into another PDF and the result is fine. Ghostscript is correctly installed and test pages are correctly printed too. Other filetypes like djvu are correctly printed, so it appears as a specifically PDF issue.
Does anyone know how to fix this issue?
UPDATES. Also PostScript files behave like PDF.