Hi Marek,
At present we do not have support for “Converting PDF to PDF/A-2B and PDF/A-3B” and we have already logged a feature request for this and we have planed to implement this feature in our upcoming Volume 1 release 2020 which is expected to available by March, 2020 tentatively. We will let you know once the feature is implemented. The status of implementation can be tracked through our Feature Management System:
PDF to PDF/A-2B : https://www.syncfusion.com/feedback/2572/convert-existing-pdf-to-pdf-a-2-conformance-document
Please let us know if you have any concerns on this.
Regards,Sowmiya Loganathan