PDFPages Signature Option – What Does It Mean?

Question

My issue

I have an A5 pdf that I want to print in order to make a booklet made of folded A4 sheets:

(source)

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My trials

I use this code to generate the pdf-to-be-printed-as-is:

\documentclass[a4paper]{article}
\begin{document}
    \includepdf[pages=-, 
            nup=1x2,
            noautoscale,
            signature=16, 
            landscape,
            delta=0 0cm]{myA5pdf}
\end{document}

Bonus: a MWE for an 8 pages A5 document

\documentclass{scrartcl}
        \usepackage[a5paper,twoside]{geometry}
\begin{document}
        \begin{Huge}
        1\clearpage
        2\clearpage
        3\clearpage
        4\clearpage
        5\clearpage
        6\clearpage
        7\clearpage
        8\clearpage
        \end{Huge}
\end{document}

However, I think I do not understand the meaning (and the functioning) of the signature option.

I have read the documentation and this post that say:

signature Creates booklets by rearranging pages into signatures and setting nup=1×2 or nup=2×1, respectively. This option takes one argument specifying the size of the signature, which should be a multiple of 4.

but the meaning is then no clearer for me.

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My questions

So my questions are:

1. What is the meaning of signature?
2. Which argument (multiple of 4) should I chose:
   • when myA5pdf has 4*n pages?
   • when myA5pdf has 4*n+2 pages?

Answer 1

In the context of bookbinding, signature equals (even if technically incorrect) sections, that are not our beloved hierarchical level #1, but rather booklets that are then stitched together to form a book. (source - you can see here a book made of about 50 signatures (i.e. booklets))

In the context of pdfpages, the argument of the option signature refers to the amount of pages of the original pdf you want to have per section (hence a multiple of 4). Here the example of the influence of signature when importing a 16 pages document: