I only added one more table so that the text would be limited to the size of the email. additionally for the class you want to make sure to have mkteditable by itself in the class.
<!-- content -->
<table width="100%">
<tr>
<td>
<div class="content">
<table class="mktEditable" id="center-content" align=center width="600">
<tr>
<td style="margin:0px 0px 10px 0px;">
<p class="mktEditable" id="other" style="text-align: center;">Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et.</p>
<!-- A Real Hero (and a real human being) -->
<p><img src="http://na-ab03.marketo.com/rs/the451group/images/580x195_box.jpg" alt="image"/></p><!-- /hero -->
<p class="mktEditable" id="other1" >Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. </p>
</td>
</tr>
</table>
<table class="button" style="width:50%; margin: 0px auto 20px auto;">
<tr>
<td style="border: 1px solid #6F1200">
<a class="mktEditable" id="button_title" href="#">Read the full press release</a>
</td>
</tr>
</table>
</div>
<!-- /content -->
<hr align="center" width="580px" style="background-color:#4d4f53; margin-bottom:0px;">
<!-- /content -->
<div class="content">
<table bgcolor="#EEEEEE" align="center" width="580px">
<tr>
<td>
<!-- Achievements -->
<table class="social">
<tr>
<td>
<div class="content">
<table class="mktEditable" id="achievements">
<tr>
<td>
<p> </p>
<h6 style="margin: -10px 0px 0px 25px;"><strong>Achievements</strong></h6>
<p class="" style="color:#4D4F53; margin:10px 0px 0px 25px;">
<strong>Subject Text:</strong><br>
<a href="#">Text Link</a><br>
<a href="#">Text Link</a><br>
<a href="#">Text Link</a><br>
</p>
<p class="" style="color:#4D4F53; margin: 10px 0px 20px 25px;">
<strong>Subject Text:</strong><br>
<a href="#">Text Link</a><br>
<a href="#">Text Link</a><br>
<a href="#">Text Link</a><br>
</p>
</td>
</tr>
</table>
</div>
<div class="clear"></div>
</td>
</tr>
</table>
<!-- Achievements -->
</td>
</tr>
</table>
</div>
<!-- /content -->
</td>
</tr>
</table>
<hr align="center" width="580px" style="background-color:#4d4f53; margin-top:0px;">
PS.. you also want to be careful with margins because some email clients don't like them **Cough cough Microsoft cough cough**