function FormCanRedo: Boolean;
FormCanRedo wraps PDFium's FORM_CanRedo. It returns
True when the FOCUSED AcroForm widget has at least one
undone edit in its redo stack that FormRedo could
re-apply, and False otherwise.
Returns False safely when the view is inactive, the
document has no AcroForm, or no widget is focused.
Making a fresh edit (typing, paste, etc.) clears the redo stack
— FormCanRedo flips to False after the next edit.
This matches the standard text-editor convention.
if PdfView1.FormCanRedo then
PdfView1.FormRedo
else
Beep;