Dear Andreas, thanks, I think you answered my question and it is a problem with helvetica font, that every letter has the same width. Therefore it seem when I try to center the textposition with
float textPosition = pageCenter.x - (font.getWidth("12")/2); that my text is not centered because the "1" needs less space than a "3" for example in Helvetica. I see that there is an included resource in PDFbox for ArialMT. How can I load this font? How can I answer a reply in this mailing list? I don't get your mail in my inbox. Thanks!