PDF/A standard is ideally preferred for archiving and long-term preservation of electronic documents. To output PDF files from PDF Converter app that conform to PDF/A, enable the ‘PDF/A Compliant‘ option available under context menu > PDF Output Settings… > Pdf Output tab. By default, this option is not enabled.
NOTE: PDF/A output is only supported when documents are outputted as individual or separate PDF files. It does not work when you combine documents into one PDF file.