public string Password {get; set;}

//This example demonstrates how to export a layout to PDF.

//Added references
using ArcGIS.Desktop.Core;                         //Project
using ArcGIS.Desktop.Layouts;                      //Layout classes
using ArcGIS.Desktop.Framework.Threading.Tasks;    //QueuedTask
using ArcGIS.Desktop.Mapping;                      //Export formats

public class ExportLayoutToPDFExample
{
  public static Task ExportLayoutToPDFAsync(string LayoutName, string Path)
  {
    //Reference a layoutitem in a project by name
    LayoutProjectItem layoutItem = Project.Current.GetItems<LayoutProjectItem>().FirstOrDefault(item => item.Name.Equals(LayoutName));
    if (layoutItem == null)
      return Task.FromResult<Layout>(null);

    //Create PDF format with appropriate settings
    PDFFormat PDF = new PDFFormat();
    PDF.Resolution = 300;
    PDF.OutputFileName = Path;
    //PDF.Password = "xxx";

    return QueuedTask.Run(() =>
    {
            //Export Layout
            Layout lyt = layoutItem.GetLayout(); //Loads and returns the layout associated with a LayoutItem
            if (PDF.ValidateOutputFilePath())
      {
        lyt.Export(PDF);
      }
    });
  }
}

//This example demonstrates how to export an individual map frame on a layout to PDF.

//Added references
using ArcGIS.Desktop.Core;                         //Project
using ArcGIS.Desktop.Layouts;                      //Layout classes
using ArcGIS.Desktop.Framework.Threading.Tasks;    //QueuedTask
using ArcGIS.Desktop.Mapping;                      //Export formats

public class ExportMapFrameToPDFExample
{
  public static Task ExportMapFrameToPDFAsync(string LayoutName, string MFName, string Path)
  {
    //Reference a layoutitem in a project by name
    LayoutProjectItem layoutItem = Project.Current.GetItems<LayoutProjectItem>().FirstOrDefault(item => item.Name.Equals(LayoutName));
    if (layoutItem == null)
      return Task.FromResult<Layout>(null);

    //Create PDF format with appropriate settings
    PDFFormat PDF = new PDFFormat();
    PDF.Resolution = 300;
    PDF.OutputFileName = Path;
    //PDF.Password = "xxx";

    return QueuedTask.Run(() =>
    {
            //Export MapFrame
            Layout lyt = layoutItem.GetLayout(); //Loads and returns the layout associated with a LayoutItem
            MapFrame mf = lyt.FindElement(MFName) as MapFrame;
      PDF.OutputFileName = Path;
      if (PDF.ValidateOutputFilePath())
      {
        mf.Export(PDF);
      }
    });
  }
}