There is a special version of PD4ML with PDF/A output support: PD4ML Volume DMS Edition (starting from v360).  The version introduces a new PD4ML API call generatePdfa(boolean enable).

In PDF/A output mode PD4ML generates all needed document metadata and disables some features, which are not allowed by PDF/A format: for example document encryption. Also PDF/A requires all used fonts are embedded into the resulting PDF. If TTF embedding is not switched on, PD4ML in PDF/A mode implicitly enables it and embeds default TTF fonts.

PDF/A generation mode requires pd4ml_rc.jar is in the same directory where pd4ml.jar is.

PDF/A generation errors or warnings may be obtained this way (after pd4ml.render() all)

PD4ML.StatusMessage[] msgs =
(PD4ML.StatusMessage[]) pd4ml.getLastRenderInfo(PD4Constants.PD4ML_PDFA_STATUS);

for ( int i = 0; i < msgs.length; i++ ) {
System.out.println( (msgs[i].isError() ? "ERROR: " : "WARNING: ") + msgs[i].getMessage());