Add Barcodes to Existing PDF

using Opait.Barcoder.Api;

// Creates a PDF417 barcode and adds it to all pages of a PDF file.
static void AddBarcodeToPdf(string message, string sourceFile, string destFile)
{
    // Initialize the barcoder library with default options.
    var barcoder = new Barcoder();

    // Create a barcode encoder of the specified type and content.
    var encoder = barcoder.CreateEncoder(BarcodeType.PDF417, message);

    // Create a PDF renderer for saving generated barcodes.
    var renderer = barcoder.CreatePdfRenderer();

    // Open the source PDF file and create a new destination PDF
    using (var srcPdf = barcoder.OpenPdfDocument(sourceFile))
    using (var dstPdf = barcoder.CreatePdfDocument())
    {
        // Save pages as we modify them to reduce memory requirements.
        dstPdf.BeginSave(destFile);

        // Go through each page of source PDF
        for (var i = 0; i < srcPdf.PageCount; i++)
        {
            // Get the source page
            var srcPage = srcPdf.GetPage(i);

            // Add a copy of the source page to the destination PDF
            var dstPage = dstPdf.AddPage(srcPage);

            // Get the bounding rectangle of the page.
            var bounds = dstPage.CropBox;

            // Append the barcode to the existing content of the page.
            // Remember that PDF boxes are not inverted. (X,Y) is bottom left corner.
            renderer.RenderBarcode(dstPage, encoder, bounds.X + 5, bounds.Y + 5, 120, 40);

            // Save the page.
            dstPdf.SavePage(dstPage);
        }

        // Complete saving of the entire document.
        dstPdf.EndSave();
    }
}