Hi,

Please refer below code.

C#

Document Doc = new Document(new Rectangle(288f, 144f), 10, 10, 10, 10);
Doc.SetPageSize(iTextSharp.text.PageSize.A4.Rotate());

You might also need this to expand a table to max width.

var _pdf_table = new PdfPTable(2); // table with two  columns
PdfPCell hc = new PdfPCell();
_pdf_table.WidthPercentage = 100; //table width to 100per
_pdf_table.SetTotalWidth(new float[] { 25, iTextSharp.text.PageSize.A4.Rotate().Width - 25 });

also you can refer below link

http://stackoverflow.com/questions/2019246/itextsharp-table-in-landscape

I hope this will help you out.