I've added a small Java example to the iText site showing how it's done: SimpleRowColspan
As you can see, the result looks very much like the table you describe. I'm not sure what you mean when you say your searches didn't result in finding an example that helped you. Maybe you're looking for a C# example instead of a Java example? Maybe you found the example that accompanies the book I wrote, MyFirstTable, but didn't find its C# counterpart.
Although I'm not a C# developer, that would look like this:
PdfPTable table = new PdfPTable(5);
float[] widths = new float[] { 1f, 2f, 2f, 2f, 1f };
table.SetWidths(widths);
PdfPCell cell;
cell = new PdfPCell(new Phrase("S/N"));
cell.Rowspan = 2;
table.AddCell(cell);
cell = new PdfPCell(new Phrase("Name"));
cell.Colspan = 3;
table.AddCell(cell);
cell = new PdfPCell(new Phrase("Age"));
cell.Rowspan = 2;
table.AddCell(cell);
table.AddCell("SURNAME");
table.AddCell("FIRST NAME");
table.AddCell("MIDDLE NAME");
table.AddCell("1");
table.AddCell("James");
table.AddCell("Fish");
table.AddCell("Stone");
table.AddCell("17");
This should answer your question. If not, please clarify what isn't working for you.
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