在使用GdPicture.NET控件的時候，如果想旋轉頁面并保存覆蓋原有的PDF文件，就需要用到其中的rasterisation方法，這包括處理所有輸入PDF位圖的頁面，并將這些位圖添加到新的PDF文件中。

》》》下載GdPicture.NET最新試用版

代碼如下：

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim oGdPictureImaging As New GdPicture.GdPictureImaging
        Dim oGdViewer As New GdPicture.GdViewer
        Dim RasterizedPage As Integer
        Dim PdfID As Integer
        Dim PdfImageID As Integer
        Dim CurrentPageWidth, CurrentPageHeight As Single

        oGdPictureImaging.SetLicenseNumber("XXX") 'Unlocking GdPicture.NET -> Replace XXX by a commercial or demo license KEY

        If oGdViewer.DisplayFromFile("c:\test.pdf") = GdPictureStatus.OK Then
            PdfID = oGdPictureImaging.PdfNewPdf("c:\newpdf.pdf", True) 'PDF/A
            'Adding all rasterized pages of first to output PDF
            For i As Integer = 1 To oGdViewer.PageCount
                RasterizedPage = oGdViewer.PdfRenderPageToGdPictureImage(200, i)
                If i = 2 Then 'page to rotate !!
                    oGdPictureImaging.Rotate(RasterizedPage, RotateFlipType.Rotate90FlipNone)
                End If
                PdfImageID = oGdPictureImaging.PdfAddImageFromGdPictureImage(PdfID, RasterizedPage)
                oGdPictureImaging.ReleaseGdPictureImage(RasterizedPage)
                'Drawing the image into a PDF page
                CurrentPageWidth = oGdPictureImaging.PdfGetImageWidth(PdfID, PdfImageID)
                CurrentPageHeight = oGdPictureImaging.PdfGetImageHeight(PdfID, PdfImageID)
                oGdPictureImaging.PdfNewPage(PdfID, CurrentPageWidth, CurrentPageHeight)
                oGdPictureImaging.PdfDrawImage(PdfID, PdfImageID, 0, 0, CurrentPageWidth, CurrentPageHeight)
            Next
            oGdViewer.CloseDocument()
            oGdPictureImaging.PdfEndPdf(PdfID)
        End If
    End Sub