Wordpress - Display List Of Posts Containing a Relationship Field Value [ACF]

I am updating my complete answer based on your clarification in the comment below. I hope this helps:

<div class="entry-content">

   <h2>Documents written by this writer</h2>
        <?php 
        /*
         *  Query posts for a relationship value.
         *  This method uses the meta_query LIKE to match the string "123" to the database value a:1:{i:0;s:3:"123";} (serialized array)
         */

         $documents = get_posts(array(
                     'post_type' => 'document',
                     'meta_query' => array(
                      array(
                            'key' => 'writer', // name of custom field
                            'value' => '"' . get_the_ID() . '"', // matches exaclty "123", not just 123. This prevents a match for "1234"
                            'compare' => 'LIKE'
                                )
                            )
                        ));

                        ?>
        <?php if( $documents ): ?>
             <ul>
             <?php foreach( $documents as $document ): ?>
                <li>
                   <a href="<?php echo get_permalink( $document->ID ); ?>">
                     <?php echo get_the_title( $document->ID ); ?>
                   </a>
                </li>
             <?php endforeach; ?>
            </ul>
      <?php endif; ?>

</div>