Query Regarding PDF/A-3 format

I noticed that the official ZATCA document states that invoice documents should be shared in PDF/A-3 format with embedded XML. I’m currently using the mPDF library in PHP, but it only supports PDF/A-1B, producing output with the following details:

  • Conformance:
    • Standard: PDF/A-1B
    • ISO Name: ISO 19005-1
    • Status: Not yet verified
  • Output Intent:
    • Identifier: sRGB IEC61966-2.1
    • Info: sRGB IEC61966-2.1 (with XML embedded)

Will this PDF/A-1B format cause any issues? Also, does PDF/A-3 refer to the page size? Do I need to change the invoice page width and height to meet the PDF/A-3 requirements?

Are there any PHP libraries available that support PDF/A-3?