FileName property

Path of the PDF to open; it can only be assigned whilst the component is inactive, and assigning it whilst Active is True raises EPdfError

The path is passed to PDFium as UTF-8, so folders and file names in any script work; Free Pascal builds convert from the string's own code page, so this holds as well when the program does not use the Lazarus UTF-8 string mode

Empty string means "no file" — use CreateDocument to start a blank PDF instead

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