I'd like to clarify this thread since it wasn't conclusive, and it's the only thread that I found with this issue. I stumbled upon the same issue, and the documentation isn't clear. First PDF::API2::Simple does NOT support different encoding other than the default 8-bit encoding. PDF::API2 does support unicode, but you cannot load a corefont to the PDF and then do add it using $PDF->add_font() since it's a PDF::API2::Simple method, and it can't handle different encodings. PDF::API2::Simple only allows you to load external fonts, but only with 8 bit encoding. To use different encodings you have to use the full PDF::API2 module. The best doc for a pdf newb that I found was the following:
http://pdfapi2.sourceforge.net/pdfapi2_for_fun_and_profit_APW2005.pdf
Cheers,
Speedy G