Represents the "Order" entry of the type 0 function dictionary
It is an optional entry defined as part of the PDF 1.0
It contains an integer representing a PDF numeric object.
It should have a minimum value of 1 and a maximum of 3.
The PDF specification states that this item assumes a value of 1
if no value has been provided.
For definitive details see:.
The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 39,
The ISO PDF
Specification, ISO 32000-2:2017 PDF 2.0; Table: 39, page 124.