아래 코드를 찾으신 다음

<div class="kboard-document-navi">
	<div class="kboard-next-document">
		<?php
		$bottom_content_uid = $content->getPrevUID();
		if($bottom_content_uid):
		$bottom_content = new KBContent();
		$bottom_content->initWithUID($bottom_content_uid);
		?>
		<a href="<?php echo esc_url($url->getDocumentURLWithUID($bottom_content_uid))?>" title="<?php echo esc_attr(wp_strip_all_tags($bottom_content->title))?>">
			<span class="navi-arrow">«</span>
			<span class="navi-document-title kboard-default-cut-strings"><?php echo wp_strip_all_tags($bottom_content->title)?></span>
		</a>
		<?php endif?>
	</div>
	
	<div class="kboard-prev-document">
		<?php
		$top_content_uid = $content->getNextUID();
		if($top_content_uid):
		$top_content = new KBContent();
		$top_content->initWithUID($top_content_uid);
		?>
		<a href="<?php echo esc_url($url->getDocumentURLWithUID($top_content_uid))?>" title="<?php echo esc_attr(wp_strip_all_tags($top_content->title))?>">
			<span class="navi-document-title kboard-default-cut-strings"><?php echo wp_strip_all_tags($top_content->title)?></span>
			<span class="navi-arrow">»</span>
		</a>
		<?php endif?>
	</div>
</div>

아래 남겨드린 코드로 바꿔 보시겠어요?

<div class="kboard-document-navi">
	<div class="kboard-prev-document">
		<?php
		$bottom_content_uid = $content->getPrevUID();
		if($bottom_content_uid):
		$bottom_content = new KBContent();
		$bottom_content->initWithUID($bottom_content_uid);
		?>
		<a href="<?php echo esc_url($url->getDocumentURLWithUID($bottom_content_uid))?>" title="<?php echo esc_attr(wp_strip_all_tags($bottom_content->title))?>">
			<span class="navi-arrow">«</span>
			<span class="navi-document-title kboard-default-cut-strings"><?php echo wp_strip_all_tags($bottom_content->title)?></span>
		</a>
		<?php endif?>
	</div>
	
	<div class="kboard-next-document">
		<?php
		$top_content_uid = $content->getNextUID();
		if($top_content_uid):
		$top_content = new KBContent();
		$top_content->initWithUID($top_content_uid);
		?>
		<a href="<?php echo esc_url($url->getDocumentURLWithUID($top_content_uid))?>" title="<?php echo esc_attr(wp_strip_all_tags($top_content->title))?>">
			<span class="navi-document-title kboard-default-cut-strings"><?php echo wp_strip_all_tags($top_content->title)?></span>
			<span class="navi-arrow">»</span>
		</a>
		<?php endif?>
	</div>
</div>

바꾸셨다면 바꾼 코드에서

<span class="navi-arrow">«</span>

<span class="navi-arrow">»</span>

이 부분을 각각에 맞게 교체해보시겠어요?

고맙습니다.