Similar to these issues, but for Java and different output Format
NullReferenceException during PDF/A-1a Conversion of PDF with TextAnnotation and PopupAnnotation
System.NullReferenceException when using PdfFormat.ZUGF…...NullPointerException during conversion of PDF with formats ZUGFeRD / PDF_A_4...output format NullReferenceExcepti during PDF/A-1a conversion of...