ImportPreferences function

Bit-set controlling how ImportPages copies content (resources, named destinations, comments, etc.).

Set before calling ImportPages

Wraps the corresponding PDFium API and exposes it as a TPdf instance member so consumers do not have to manage FPDF_DOCUMENT handles directly

• Always check Pdf1.Active before calling page-scoped operations; methods that require an open document raise EPdfError otherwise
• Document-edit methods (AddPage / DeletePage / UpdatePage / CreateAnnotation) leave the in-memory document dirty — remember to call SaveToFile to persist
• Class methods (LoadLibrary / UnloadLibrary / GetRecommendedV8Flags) can be called without a TPdf instance