C++ で PDF を回転

void ChangePageOrientation() {

    String _dataDir("C:\\Samples\\");
    String inputFileName("ChangeOrientation.pdf");
    String outputFileName("ChangeOrientation_out.pdf");
    // Open document
    auto document = MakeObject<Document>(_dataDir + inputFileName);

    for (auto page : document->get_Pages())
    {

        auto r = page->get_MediaBox();
        double newHeight = r->get_Width();
        double newWidth = r->get_Height();
        double newLLX = r->get_LLX();

        //  We must to move page upper in order to compensate changing page size
        // (lower edge of the page is 0,0 and information is usually placed from the
        //  Top of the page. That's why we move lover edge upper on difference between
        //  Old and new height.

        double newLLY = r->get_LLY() + (r->get_Height() - newHeight);
        page->set_MediaBox(MakeObject<Rectangle>(newLLX, newLLY, newLLX + newWidth, newLLY + newHeight));
        // Sometimes we also need to set CropBox (if it was set in original file)
        page->set_CropBox(MakeObject<Rectangle>(newLLX, newLLY, newLLX + newWidth, newLLY + newHeight));

        // Setting Rotation angle of page
        page->set_Rotate(Rotation::on90);
    }

    // Save output file
    document->Save(_dataDir + outputFileName);
}