Printing certain characters to PDF breaks rendering, see the following example.

QPdfWriter Printer("C:/tmp/pdf.pdf");
QPainter Painter;
Printer.setPageSize(QPagedPaintDevice::A4);
Printer.setResolution(96);
Painter.begin(&Printer);
Painter.drawText(10,10, QString::fromStdString("\xe2\x96\xb2 down arrow does not work"));
Painter.drawText(10,10, QString::fromStdString("works only when previous line is commented"));
Painter.end();