PDF export does not preserve accessibility information
Authoring tools capable of exporting PDF files that conform to ISO 32000-1:2008 (PDF 1.7) MUST also be capable of exporting PDF files that conform to ANSI/AIIM/ISO 14289-1:2016 (PDF/UA-1).
When content is created with accessible content or features (such as alternative text, heading markup, table structure, etc.), those accessible features must be preserved when converting the document to PDF whenever those features are supported by PDF.
To fix this issue, ensure that all accessibility related information (that is supported by PDF) is retained when content is converted to PDF. For example, the PDF preserves:
a. Text alternatives on images. b. Heading level data. c. Table structure and header data. d. List markup data. e. Form field and label markup f. Link markup and text.