THPDFHeadlessDocument.SetSignatureFieldAppearance

procedure SetSignatureFieldAppearance(FieldIndex: Integer;
  const Caption: UnicodeString; const TrueTypeFont: SysUtils.TBytes;
  const Options: THPDFHeadlessTextAppearanceOptions;
  const ProfileName: UnicodeString = '');

Builds explicit Unicode normal appearances for every widget of a writable unsigned signature field

The caption remains separate from the cryptographic V value; signing later replaces the unsigned value with a signature dictionary

Layout, font embedding, cancellation, rotation and transactional object registration follow the shared appearance builder

A nonempty ProfileName selects an actual built-in visual configuration: HotPDF.StandardApproval, HotPDF.StandardCertification or HotPDF.Compact

The profile controls font size, alignment, padding, colour, border, wrapping and background; Options retains resource limits and cancellation, whilst the actual widget determines geometry and rotation

Unknown profile names fail before the appearance is changed; an empty name retains ordinary caller-configured appearance behaviour

A required signature seed AppearanceFilter must match a profile actually applied in the current document instance; persisted metadata alone does not establish that application after reload

A signed field cannot have its visible appearance replaced; encrypted sources require form-fill permission or owner authentication