Hey there, fresh eyes this morning and realised what i can do with this as it isnt a problem with ASP but its the parsed text thats the issue.
I have added the following to my code to strip the content area:
$pdf_asp_content = get_post_field( ‘_asp_attachment_text’, $post_id );
$sanitised_content = wp_strip_all_tags( $pdf_asp_content );
echo $sanitised_content;
this then still allows for Highlighter on the content 🙂