Accordion's hidden sections can be printed with the help of custom JavaScript passed to the setCustomJavascript API method. The code depends on the library that creates the accordion.
For jQuery UI use this code:
libPdfcrowd.insertStyle({style: '.ui-accordion-content {display: block !important}'});
For Bootstrap use this code:
libPdfcrowd.insertStyle({style: '.collapse {display: block !important}'});