hello jorma-olavi, for issues related to extensions please contact its developers directly - they likely can give you better advice & far more detailed guidance. a support e-mail address is provided at https://addons.mozilla.org/firefox/ad.../print-pages-to-pdf/.

Add-on group informed me that "I was using one of the rare cases where Add-on have to produce a graphic instead of a pure pdf. That is only partially supported." They are trying to find solution later on.

So this problem is SOLVED.

But I couldn't find at this answer page, where to put "SOLVED". Hopefully some-one can advice me for next case ? yours jorma-olavi