using System;
using Microsoft.Office.Interop.Excel;

namespace officeInterop
{
    class Program
    {
        static void Main(string[] args)
        {
            Application app = new Application();
            Workbook wkb = app.Workbooks.Open("d:\x.xlsx");
            wkb.ExportAsFixedFormat(XlFixedFormatType.xlTypePDF, "d:\x.pdf");
        }
    }
}