How can I set an A4 document in landscape (horizontal) format in iTextSharp?
You can set the page size to a rotated A4. E.g. (assuming PDF, but should apply regardless):
iTextSharp.text.Document doc;
// ...initialize 'doc'...
// Set the page size
doc.SetPageSize(iTextSharp.text.PageSize.A4.Rotate());
I've done this with PDF without trouble, haven't tried it with other doc types.