Creates a new document holding the pages of this document that pages selects.
public PdfDocument ExtractPages(Range pages)
The 0-based page indices, such as 0..3 for the first three pages; at least one page.
ISO 32000-2 §7.7.3, §12.3, §12.4.2 and §14.7. A new PDF 2.0 document to which the pages are appended as AppendPages(PdfDocument, Range) appends them: it keeps the outline items that show those pages (and the items above them), the named destinations and form fields on them, their page labels, and the structure elements whose content is on them (pruned of content on other pages). This document is only read.