I have not found where to set this setting. I have really tried, maybe it does not exist.
Cheers.
There is a configuration option to handle this export formatting when you are using ExcelML export.
Configure the ExportSettings for your AJAX Grid similar to the following:
<ExportSettings ExportOnlyData="true" OpenInNewWindow="true" Excel-Format="ExcelML" />
Handle the OnExcelMLWorkBookCreated event, and you can set the papersize with the following property:
protected void grid_ExcelMLWorkBookCreated(object sender, Telerik.Web.UI.GridExcelBuilder.GridExcelMLWorkBookCreatedEventArgs e)
{
e.WorkBook.Worksheets[0].WorksheetOptions.Print.PaperSize = System.Drawing.Printing.PaperKind.A4;
}
Here is a link to the RadGrid ExcelML Export documentation.