Begins a marked-content sequence with an inline property list (BDC), such as an artifact's Type and Subtype.
public void BeginMarkedContent(string tag, CosDictionary properties)
The tag: the role of the sequence, such as Artifact or a structure type.
The property list, written inline: it shall hold direct objects only, and no MCID.
ISO 32000-2 §14.6.1, Table 352, §14.6.2 (property lists) and §14.8.2.2.2, Table 363 (artifact property lists). Tagged content
(an MCID linked into the structure tree) is begun with BeginTaggedContent(PdfStructureElement), which
allocates the MCID; artifacts with BeginArtifact(); optional content with BeginOptionalContent(PdfOptionalContentGroup).