property PageCount: Integer;
Returns the total number of pages in the open document. The value is sourced from the page dictionary in the PDF, after any inherited /MediaBox / /CropBox / /Rotate from parent nodes are resolved.
Read-only unless the property name implies a writer (such as Page or PageRotation); assigning to read-only properties has no effect.
Coordinates and dimensions are reported in PDF user-space points. To convert to pixels for a target DPI, use PointsToPixels(Value, DPI) or the equivalent helpers.
Pdf1.Page; switching the current page transparently updates the values returned here.Active is False the property returns 0, an empty rectangle, or the default enum element.
if Pdf1.Active then
Memo1.Lines.Add('PageCount = ' + VarToStr(Pdf1.PageCount));