How can I add a named destination to a specific line of a pdf file?

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C#

PDF

In my C# project, I want to read a pdf file line by line, and when the line contains a specific string, I want to add a named destination to this line (not to the page).

What I have tried:

I have found the following example, but this is adding destination to outlines. How can I adapt this to specific lines?

static void Main(string[] args)
{
    String InputPdf = @"test.pdf";
    String OutputPdf = "out.pdf";

    PdfDocument pdfDoc = new PdfDocument(new PdfReader(InputPdf), 
                         new PdfWriter(OutputPdf));

    PdfOutline outlines = pdfDoc.GetOutlines(false);
    // first level     
    foreach (var outline in outlines.GetAllChildren())
    {
        // second level
        foreach (var second in outline.GetAllChildren())
        {
            String title = second.GetTitle();
            PdfDestination dest = second.GetDestination();

            pdfDoc.AddNamedDestination(title, dest.GetPdfObject());
        }
    }
    pdfDoc.Close();
}