Hello,
You need to set custom margins if you don't want to use the default values of the chosen paper type when creating sections using addSection (phpdocx_section tag):
<phpdocx_section data-paperType="A4-landscape" data-sectionType="nextPage" data-marginTop="850" data-marginRight="1077" data-marginBottom="850" data-marginLeft="1077" />
About your other question, because of how sections work you only can generate one section for each embedHTML method call, for example:
$html = '
<phpdocx_modifypagelayout data-paperType="A4" data-marginTop="850" data-marginRight="1077" data-marginBottom="850" data-marginLeft="1077" />
<p>Paragraph 1</p>
<p>Paragraph 2</p>
';
$docx->embedHTML($html, array('useHTMLExtended' => true));
$html = '
<phpdocx_section data-paperType="A4-landscape" data-sectionType="nextPage" data-marginTop="850" data-marginRight="1077" data-marginBottom="850" data-marginLeft="1077" />
<p>Paragraph A</p>
<p>Paragraph B</p>
';
$docx->embedHTML($html, array('useHTMLExtended' => true));
$html = '
<phpdocx_section data-paperType="A4" data-sectionType="nextPage" data-marginTop="850" data-marginRight="1077" data-marginBottom="850" data-marginLeft="1077" />
<p>Paragraph I</p>
<p>Paragraph II</p>';
$docx->embedHTML($html, array('useHTMLExtended' => true));
$html = '
<phpdocx_section data-paperType="A4-landscape" data-sectionType="nextPage" data-marginTop="850" data-marginRight="1077" data-marginBottom="850" data-marginLeft="1077" />
<p>Paragraph a</p>
<p>Paragraph b</p>
';
$docx->embedHTML($html, array('useHTMLExtended' => true));
We have moved a request to add support to generating multiple sections in the same embedHTML method to the dev team.
Regards.