Hello,
The formsfields option available in the conversion plugin based on LibreOffice is false as default (https://www.phpdocx.com/api-documentation/format-conversion/convert-Word-docx-into-pdf-with-PHP).
If you want to use this option, you need to add macro in your LibreOffice home folder and enable the option when calling transformDocument.
Please check the macros-libreoffice folder included in the package. In this folder you can read all information about adding and using macros with the conversion plugin based on LibreOffice.
Regards.