Convert arabic"unicode" content html or xml to pdf using itextsharp

You need to use container elements which support RunDirection, such as ColumnText or PdfPCell and then set their element.RunDirection = PdfWriter.RUN_DIRECTION_RTL

List<IElement> list = HTMLWorker.ParseToList(new StringReader(resultCache), ST);
doc.Open();

//Use a table so that we can set the text direction
PdfPTable table = new PdfPTable(1);
//Ensure that wrapping is on, otherwise Right to Left text will not display
table.DefaultCell.NoWrap = false;
table.RunDirection = PdfWriter.RUN_DIRECTION_RTL;

//Loop through each element, don't bother wrapping in P tags
foreach (var element in list)
{
    //Create a cell and add text to it
    PdfPCell text = new PdfPCell(new Phrase(element, font));

    //Ensure that wrapping is on, otherwise Right to Left text will not display
    text.NoWrap = false;

    //Add the cell to the table
    table.AddCell(text);
}
//Add the table to the document
document.Add(table);
doc.Close();
pdfWriter.Close();

For addition reference, have a look at this sample.