using Microsoft.Office.Core;
using Microsoft.Office.Interop.PowerPoint;

///summary>       
/// 把PowerPoint文件转换成PDF格式文件      
////summary>       
///param name="sourcePath">源文件路径/param>    
///param name="targetPath">目标文件路径/param>
///returns>成功返回true,失败返回false/returns>
public static bool PPTConvertToPDF(string sourcePath, string targetPath)
{
        bool result;
        PpSaveAsFileType ppSaveAsFileType = PpSaveAsFileType.ppSaveAsPDF;//转换成pdf
        object missing = Type.Missing;
        Microsoft.Office.Interop.PowerPoint.ApplicationClass application = null;
        Presentation persentation = null;
        try
        {
            application = new Microsoft.Office.Interop.PowerPoint.ApplicationClass();
            persentation = application.Presentations.Open(sourcePath, MsoTriState.msoTrue, MsoTriState.msoFalse, MsoTriState.msoFalse);
            if (persentation!=null)
            {
                persentation.SaveAs(targetPath, ppSaveAsFileType, MsoTriState.msoTrue);
            }
            result = true;
        }
        catch
        {
            result = false;
        }
        finally
        {
            if (persentation != null)
            {
                persentation.Close();
                persentation = null;
            }
            if (application != null)
            {
                application.Quit();
                application = null;
            }
        }
        return result;
}

OfficeToPdf.PPTToPDF("d:\\12345.pptx", "d:\\12345.pdf");