To get this topic alive again, I’ve tried the script:

// Define variables
var file = app.activeDocument;
var pages = file.pages;
var numberOfPages = pages.length;

// Duplicate each page
for (i = 0; i < numberOfPages; i++) {
file.pages[i].duplicate();
}

// Intertwine pages
for (var i = 0; i < (numberOfPages – 1); i++) {
var currentPage = (numberOfPages + i);
var insertPoint = (i + i);

file.pages[currentPage].move(LocationOptions.AFTER, file.pages[insertPoint]);
}

The only problem is that I get an syntax error