Unable to update the pdf version to 1.7

[Nonudeveloper]

Bug Report

Description of the problem

I am unable to update the pdf version to 1.7

Code sample

let pdf = new PDFDocument({
size: 'LEGAL',
pdfVersion: 1.7
});

Your environment

• pdfkit version:
• Node version:
• Browser version (if applicable):
• Operating System:

[blikblum]

What happens when you set version to 1.7?

[liborm85]

Newer versions are not supported. pdfkit support only version 1.3 document structure.
Variable pdfVersion only change pdf header and use other engine for document encryption (see #820). Other elements in document are still in version 1.3.

[liborm85]

duplicate: #332