I have Ubuntu 12.04 and gimp2.8 installed. It is working fine, but gimp2.8 cannot edit any pdf file (unknown file type). This pdf files can be edited with gimp 2.6. I have installed 2.8 from the ppa:otto-kesselgulasch
Why I do not know, but I had some libgimp stuff in usr/share/loca/lib . After removing this gimp works fine and can import pdf files.