QPrinter printer;

    printer.setOutputFormat(QPrinter::PdfFormat);//设置输出格式为pdf

    printer.setPageSize(QPrinter::A4);//设置纸张大小为A4

    printer.setOutputFileName("test.pdf");//设置输出路径

    QPainter painter;
    painter.begin(&printer);

    //正常使用painter 绘制文字、pixmap等在printer上
....


    //至此，文件被保存
    painter.end();

   //文字
   painter.setFont(Nstr->font);
   painter.drawText(Nstr->pos, Nstr->str);

   //line
   QPen pen;
   pen.setWidth(Nlin->pointsize);
   painter.drawLine(Nlin->pos1 , Nlin->pos2);

   //pixmap
   //QRect rect = painter.viewport();
   //int multiple = rect.width()/Npix->pixmap.width();
   //使用scale拉伸，效果并不好，总会影响其他输出，推荐只使用Rect得到大小，让pixmap绘制到Rect内，自动填充。
   //painter.scale(multiple, multiple);
   painter.drawPixmap(Npix->rect, Npix->pixmap);

   pen.setColor(Qt::red);
   brush.setColor(Qt::red);
   brush.setStyle(Qt::SolidPattern);
   painter.setBrush(brush);
   painter.setPen(pen);
   painter.drawRect(Nrec->rect);