Pdf property

Pdf is the document source for the viewer. The viewer does not own a parser of its own — every page-, text-, image-, annotation- and form-related operation it exposes is delegated to the underlying TPdf instance pointed to by this property. Indexed properties such as Character, Bitmap, WebLink, and counters like PageCount or BitmapCount simply forward to the linked component, scoped to whatever page the viewer is currently showing.

Two usage patterns are supported. The shared pattern drops a TPdf on the form, sets Pdf to it at design time, and lets the same TPdf back several viewers, a printer routine, and a thumbnail panel from one in-memory document. The self-contained pattern leaves Pdf unassigned; the viewer creates and owns an internal TPdf the first time Active is set to True and frees it on destruction, so an application that only ever shows one document can ignore the helper component entirely.

When Pdf is changed while Active is True the viewer reloads the current page from the new source. Setting Pdf to nil on an active viewer deactivates it.

• The viewer subscribes to component notifications, so a TPdf destroyed first automatically clears this reference without leaving a dangling pointer.
• Multiple viewers can share one TPdf safely. Render and page-unload calls are serialized per TPdf instance; document mutation and component ownership still belong to the application thread that coordinates the viewer.
• Edits made through the viewer (annotation create/delete, form-field assignment, image insertion) mutate the linked TPdf, so Pdf.SaveAs after editing persists those changes.