This document is generated with PdfGenerateConfig.PdfAConformance = PdfAConformance.PdfA2A - the accessible level of PDF/A-2. It carries an embedded sRGB ICC output intent, an XMP metadata stream with pdfaid:part/pdfaid:conformance, and - because "A" levels build on tagged-PDF output - the same logical structure tree the Tagged PDF showcase demonstrates.
PDF/A-1 (not shown here) forbids PDF transparency groups entirely - PeachPDF rejects a document that uses CSS/SVG opacity, an SVG mask, or a semi-transparent gradient stop under that level rather than silently producing a non-conformant file. PDF/A-2 and PDF/A-3, used here, permit transparency normally.