The pdfd:conformsTo URI declaring Well-Tagged PDF 1.0's conformance level for reuse, as veraPDF's WTPDF 1.0 Reuse profile
tests it (rule 6.1.2-1); a save writes it for Reuse.
public const string WellTaggedReuse = "http://pdfa.org/declarations/wtpdf#reuse1.0"
WTPDF 1.0 §6.1.2. The specification's text spells the URI with a slash before the fragment (wtpdf/#reuse1.0); veraPDF,
the validator the output is checked with, tests for this spelling (declarations.contains(...), an exact match).