Extract pages from a PDF in C#

using GdPicture14;

LicenseManager license = new LicenseManager();
license.RegisterKEY("");

using GdPicturePDF gdpicturePDF = new GdPicturePDF();
using GdPicturePDF gdpictureDestPDF = new GdPicturePDF();
gdpicturePDF.LoadFromFile(@"input.pdf");
gdpictureDestPDF.NewPDF();
// Extract specified pages to the output file.
gdpictureDestPDF.ClonePages(gdpicturePDF, "2-3;5");
gdpictureDestPDF.SaveToFile(@"output.pdf");

Imports System.IO
Imports GdPicture14

Dim license As LicenseManager = New LicenseManager()
license.RegisterKEY("")

Using gdpicturePDF As GdPicturePDF = New GdPicturePDF()
Using gdpictureDestPDF As GdPicturePDF = New GdPicturePDF()
    gdpicturePDF.LoadFromFile("input.pdf")
    gdpictureDestPDF.NewPDF()
    ' Extract specified pages to the output file.
    gdpictureDestPDF.ClonePages(gdpicturePDF, "2-3;5")
    gdpictureDestPDF.SaveToFile("output.pdf")
End Using
End Using

using GdPictureImaging gdpictureImaging = new GdPictureImaging();
int sourceImageID;
int outputID = 0;
int imageID;
string source = @"multipage-tiff.tif", output = @"output.tif";
sourceImageID = gdpictureImaging.CreateGdPictureImageFromFile(source);
// Set the page numbers you want to extract.
int[] pages = { 1, 3, 5 };
bool firstPage = true;
foreach (int page in pages)
{
    Stream pStream = new MemoryStream();
    gdpictureImaging.TiffExtractPage(sourceImageID, page, pStream);
    // Move to the start of the stream before reading the extracted page.
    pStream.Position = 0;
    imageID = gdpictureImaging.CreateGdPictureImageFromStream(pStream);
    if (firstPage)
    {
        // If it's the first image, create a new multipage TIFF file.
        outputID = imageID;
        gdpictureImaging.TiffSaveAsMultiPageFile(outputID, output, TiffCompression.TiffCompressionAUTO);
        firstPage = false;
    }
    else
    {
        // If it's the second or later image, add to the previously created multipage TIFF file.
        gdpictureImaging.TiffAddToMultiPageFile(outputID, imageID);
        gdpictureImaging.ReleaseGdPictureImage(imageID);
    };
}
gdpictureImaging.TiffCloseMultiPageFile(outputID);
gdpictureImaging.ReleaseGdPictureImage(outputID);
gdpictureImaging.ReleaseGdPictureImage(sourceImageID);

Using gdpictureImaging As GdPictureImaging = New GdPictureImaging()
Dim sourceImageID As Integer
Dim outputID = 0
Dim imageID As Integer
Dim source = "multipage-tiff.tif", output = "output.tif"
sourceImageID = gdpictureImaging.CreateGdPictureImageFromFile(source)
' Set the page numbers you want to extract.
Dim pages = {1, 3, 5}
Dim firstPage = True
For each page In pages
    Dim pStream As Stream = New MemoryStream()
    gdpictureImaging.TiffExtractPage(sourceImageID, page, pStream)
    ' Move to the start of the stream before reading the extracted page.
    pStream.Position = 0
    imageID = gdpictureImaging.CreateGdPictureImageFromStream(pStream)
    If firstPage Then
        ' If it's the first image, create a new multipage TIFF file.
        outputID = imageID
        gdpictureImaging.TiffSaveAsMultiPageFile(outputID, output, TiffCompression.TiffCompressionAUTO)
        firstPage = False
    Else
        ' If it's the second or later image, add to the previously created multipage TIFF file.
        gdpictureImaging.TiffAddToMultiPageFile(outputID, imageID)
        gdpictureImaging.ReleaseGdPictureImage(imageID)
    End If
Next
gdpictureImaging.TiffCloseMultiPageFile(outputID)
gdpictureImaging.ReleaseGdPictureImage(outputID)
gdpictureImaging.ReleaseGdPictureImage(sourceImageID)
End Using