Hi again!
Finally I edit my code and works!
This is the code:
<?php if(have_rows('otros_archivos')):
while (have_rows('otros_archivos')) : the_row();
$post_object = get_sub_field('antecedente');
if($post_object):
$post = $post_object; setup_postdata($post); ?>
<a href="<?php the_permalink(); ?>" target="_blank"><?php the_title(); ?></a>
<br/><br/>
<?php wp_reset_postdata();
else:
echo "<i>No se ha incluido ningún antecedente aún.<br/></i>";
endif;
endwhile;
endif; ?>
Anyway thanks for your help James.
I hope this code can help someone!