the pdf library can not render unicode characters, for example, greek letters.
Code tested:

import processing.pdf.*;
size(600,800);
background(255);
beginRecord(PDF,"test.pdf");
PFont arial = createFont("Arial",48);
textFont(arial);
textSize(10);
fill(0);
text("\u03B1",50,50);
text("\u0391",50,70);
endRecord();

i can see the letters in the screen, but get an empty PDF file.
processing version:0135beta.

*** This bug has been marked as a duplicate of 727 ***