Hello,
mergeDocx doesn't change document contents (except the mergeType option to preserve or remove sections).
The DOCX documents to be merged must include the contents you want to merge.
You can use the pageNumberType option available in addSection and modifyPageLayout methods to set a custom page number format (such as a custom start number for page numbering). For example, from LayoutAndGeneral/addSection/sample_2.php included in all packages:
$docx->addSection('nextPage', 'A4', array('pageNumberType' => array('fmt' => 'lowerRoman', 'start' => 12)));
The addSection method generates a new section. If you need to change existing sections, you can use modifyPageLayout.
Regards.