For each PDF/A-1 validation issue we try to explain what it means and, if possible how to resolve it. For a more technical explanation of the issue we quote the related section of the ISO 19005-1 PDF/A Specification.
The document contains an operator that is undefined.
How can I fix it?
Use a PDF creation product that correctly defines all operators. We recommend Solid PDF Creator Plus.
6.2.10 - ISO 19005-1 PDF/A Specification:
A content stream shall not contain any operators not defined in PDF Reference even if such operators are bracketed by the BX/EX compatibility operators. Use of the ri operator shall conform to the rules of 6.2.9.
NOTE 1: Content streams are used for page descriptions, e.g. the Contents stream of a page object or the stream of a form XObject, as well as for the appearance stream of annotations, including form fields or Widget annotations.
NOTE 2: In earlier versions of the PDF format a PostScript operator PS was defined. As this operator is not defined in PDF Reference its use is implicitly prohibited by 6.2.10.