Jozef,

>2. The problem(?) of changing the PDF format is not a problem for producers of report designers at last it did not stop them as regard as using PDF outupt in their products. Acrobat Reader must be backward compatible so change in PDF specification will not kill PDF files already prepared.

That's why writing a PDF output creator is much easier than writing a PDF reader/viewer, since the reader/viewer must deal with features of many versions while for PDF output you can in most cases use a simpler set of features.