code: public void setUnicodeFileName(String filename, boolean unicode) {
          put(PdfName.UF, new PdfString(filename, unicode ? PdfObject.TEXT_UNICODE : PdfObject.TEXT_PDFDOCENCODING));
      }
docs: Adds the unicode file name (the key /UF). This entry was introduced
  in PDF 1.7. The filename must have the slash and backslash escaped
  according to the file specification rules.
  @param filename	the filename
  @param unicode	if true, the filename is UTF-16BE encoded; otherwise PDFDocEncoding is used;