Public Shared Sub DocumentAuthentication(document As Vintasoft.Imaging.Pdf.PdfDocument, password As String)
    ' document is encryptred?
    If document.AuthorizationResult = Vintasoft.Imaging.Pdf.Security.AuthorizationResult.AuthenticationNotRequired Then
        System.Console.WriteLine("Document is not encrypted.")
        Return
    End If

    ' executes authentication
    If document.AuthorizationResult = Vintasoft.Imaging.Pdf.Security.AuthorizationResult.IncorrectPassword Then
        document.Authenticate(password)
    End If

    ' check authorization result
    If document.AuthorizationResult = Vintasoft.Imaging.Pdf.Security.AuthorizationResult.IncorrectPassword Then
        System.Console.WriteLine("The password is incorrect.")
    Else
        System.Console.Write("Authentication pass successfully, ")
        If document.AuthorizationResult = Vintasoft.Imaging.Pdf.Security.AuthorizationResult.OwnerPassword Then
            System.Console.WriteLine("owner password identified.")
        ElseIf document.AuthorizationResult = Vintasoft.Imaging.Pdf.Security.AuthorizationResult.UserPassword Then
            System.Console.WriteLine("user password identified.")
        ElseIf document.AuthorizationResult = (Vintasoft.Imaging.Pdf.Security.AuthorizationResult.UserPassword Or Vintasoft.Imaging.Pdf.Security.AuthorizationResult.OwnerPassword) Then
            System.Console.WriteLine("user and owner passwords are equal.")
        End If
    End If
End Sub

public static void DocumentAuthentication(Vintasoft.Imaging.Pdf.PdfDocument document, string password)
{
    // document is encryptred?
    if (document.AuthorizationResult == 
        Vintasoft.Imaging.Pdf.Security.AuthorizationResult.AuthenticationNotRequired)
    {
        System.Console.WriteLine("Document is not encrypted.");
        return;
    }

    // executes authentication
    if (document.AuthorizationResult ==
        Vintasoft.Imaging.Pdf.Security.AuthorizationResult.IncorrectPassword)
    {
        document.Authenticate(password);
    }

    // check authorization result
    if (document.AuthorizationResult == 
        Vintasoft.Imaging.Pdf.Security.AuthorizationResult.IncorrectPassword)
    {
        System.Console.WriteLine("The password is incorrect.");
    }
    else
    {
        System.Console.Write("Authentication pass successfully, ");
        if (document.AuthorizationResult == Vintasoft.Imaging.Pdf.Security.AuthorizationResult.OwnerPassword)
            System.Console.WriteLine("owner password identified.");
        else if (document.AuthorizationResult == Vintasoft.Imaging.Pdf.Security.AuthorizationResult.UserPassword)
            System.Console.WriteLine("user password identified.");
        else if (document.AuthorizationResult == (Vintasoft.Imaging.Pdf.Security.AuthorizationResult.UserPassword | 
            Vintasoft.Imaging.Pdf.Security.AuthorizationResult.OwnerPassword))
            System.Console.WriteLine("user and owner passwords are equal.");
    }
}