+2  A: 

I did come across header and footer configuration iptions options in the firefox gui to remove your troublesome headers. I wonder if you set these, the printPDF extension will work as you want them?

singingfish
I could do the same as well - just do not have English firefox to tell you for sure that this is called "format printing" or something else.
weismat
Yes, disabling it in the GUI turned it off on the rendered PDFs.
ashgromnies