UncheckPersonalInformationRemoval.cs

//dlls in C:\Program Files (x86)\Microsoft Visual Studio 12.0\Visual Studio Tools for Office\PIA\Office15
using Microsoft.Office.Interop.Word;
using Microsoft.Office.Core;

Application wordApp = null;

try
{
    //open a new word process
    wordApp = new Application();
    wordApp.Visible = false;

    Document doc = wordApp.Documents.Open(filePath,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing,
        Type.Missing);

    if(doc.RemovePersonalInformation)
    {
        //update document, save and close
        doc.RemovePersonalInformation = false;
        doc.Close(WdSaveOptions.wdSaveChanges, Type.Missing, Type.Missing);
    }
    else
        doc.Close(WdSaveOptions.wdDoNotSaveChanges, Type.Missing, Type.Missing);
}
catch(Exception ex)
{
}
finally
{
    //close the word process
    wordApp.Quit(WdSaveOptions.wdDoNotSaveChanges, Type.Missing, Type.Missing);
}