how to work with Word Document in the C#
public class CodeImpersonate
{
    /// <summary>
    /// This logon type is intended for users who will be interactively using the computer, such as a user being logged on by a terminal server,
    /// remote shell, or similar process. This logon type has the additional expense of caching logon information for disconnected operations; therefore,
    /// it is inappropriate for some client/server applications, such as a mail server.
    /// </summary>
    public const int LOGON32_LOGON_INTERACTIVE = 2;
    /// <summary>
    /// Use the standard logon provider for the system. The default security provider is negotiate,
    /// unless you pass NULL for the domain name and the user name is not in UPN format. In this case, the default provider is NTLM.
    /// Windows 2000: The default security provider is NTLM.
    /// </summary>
    public const int LOGON32_PROVIDER_DEFAULT = 0;

    WindowsImpersonationContext impersonationContext;

    [DllImport("advapi32.dll")]
    public static extern int LogonUserA(String lpszUserName,
                                        String lpszDomain,
                                        String lpszPassword,
                                        int dwLogonType,
                                        int dwLogonProvider,
                                        ref IntPtr phToken);

    [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern int DuplicateToken(IntPtr hToken, int impersonationLevel, ref IntPtr hNewToken);

    [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern bool RevertToSelf();

    [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
    public static extern bool CloseHandle(IntPtr handle);

    public bool ImpersonateValidUser(String userName, String domain, String password)
    {
        WindowsIdentity tempWindowsIdentity;
        IntPtr token = IntPtr.Zero;
        IntPtr tokenDuplicate = IntPtr.Zero;

        if (RevertToSelf())
        {
            if (LogonUserA(userName, domain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref token) != 0)
            {
                if (DuplicateToken(token, 2, ref tokenDuplicate) != 0)
                {
                    tempWindowsIdentity = new WindowsIdentity(tokenDuplicate);
                    impersonationContext = tempWindowsIdentity.Impersonate();
                    if (impersonationContext != null)
                    {
                        CloseHandle(token);
                        CloseHandle(tokenDuplicate);
                        return true;
                    }
                }
            }
        }
        if (token != IntPtr.Zero)
            CloseHandle(token);
        if (tokenDuplicate != IntPtr.Zero)
            CloseHandle(tokenDuplicate);
        return false;
    }

    public void UndoImpersonation()
    {
        if (impersonationContext != null)
            impersonationContext.Undo();
    }

CodeImpersonate codeImpersonate = null;
try
{
    codeImpersonate = new CodeImpersonate();
    var isLoggedIn = codeImpersonate.ImpersonateValidUser(AppConfigs.OfficeUser, AppConfigs.OfficeUeerDomnia, AppConfigs.OfficeUserPass);

    if (isLoggedIn)
    {
        //Do your office work....
    }
    else
        throw new InvalidOperationException("Login failed for office user.");
}
finally
{
    if (codeImpersonate != null)
        codeImpersonate.UndoImpersonation();
    codeImpersonate = null;
}

public class ImpersonateServices
{
    public ImpersonateServices(String userName, String domain, String password)
    {
        this.UserName = userName;
        this.Domain = domain;
        this.Password = password;
    }

    public string UserName { get; private set; }

    public string Domain { get; private set; }

    public string Password { get; private set; }

    public void Execute(Action privilegedAction)
    {
        CodeImpersonate codeImpersonate = null;
        try
        {
            codeImpersonate = new CodeImpersonate();
            var isLoggedIn = codeImpersonate.ImpersonateValidUser(this.UserName, this.Domain, this.Password);

            if (isLoggedIn){
                privilegedAction();
            }
            else
                throw new InvalidOperationException("Login failed for office user.");
        }
        finally
        {
            if (codeImpersonate != null)
                codeImpersonate.UndoImpersonation();
            codeImpersonate = null;
        }
    }
}

var impersonateServices = new ImpersonateServices(AppConfigs.OfficeUser,
                                              AppConfigs.OfficeUserDomain,
                                              AppConfigs.OfficeUserPass);
impersonateServices.Execute(() => {
    //Do your Office work...
});