C # Add attachments to a database in Access

I have a database in Access that has a field of type 'Datos Ajuntos' and I would like to insert pdf files.

I have the PDF path, I just need to send it. I imagine it would be something like:

//Abrimos la conexión mas arriba    
OleDbCommand cmd = new OleDbCommand(
    string.Format("INSERT INTO MONTAÑO (MONTAÑO.[CAMPO_ARCHIVO]) VALUES('" + archivo + "')
    ,conectado
);
cmd.ExecuteNonQuery();
//Cerramos la conexión aquí abajo