I know this question has appeared before, but the earlier questions appear to be linked to the old labeling engine. I'm running qgis 2.0, which I thought uses the new-generation labeling engine. In my map there are three labels (not three layers, but just three labels) that are buffered. The pdf file grows from 1MB to 18MB by turning on buffering.
Am I wrong in thinking that 2.0 uses the new labeling engine? The rest of the team I'm working with is on 2.0 and moving everyone is not easy for a variety of reasons.