EHPDFHeadlessAppearanceError

The typed error raised by HPDFHeadlessAppearance for invalid options, malformed fonts, embedding permissions, invalid Unicode, missing glyphs, budgets and unsupported text layout

Failure yields THPDFHeadlessAppearanceFailure; the exception message describes the exact condition

Cancellation uses the existing EHPDFOperationCancelled contract, whilst document field policies and security checks use EHPDFHeadlessDocumentError