Merge all attributes of multiple PDF files using MuPDF

pdf-full-merge.js

// Merge all attributes of multiple PDF files (pdf-full-merge.js)
// Extended from MuPDF's docs/examples/pdf-merge.js

// Ever had problems with tools that don't copy certain attributes of a PDF?
// This script uses MuPDF to merge/join/concatenate as much as possible, including:
// - bookmarks / outlines / table of contents
// - link attributes of said outlines, such as viewrect and zoom
// - whether outlines appear open or closed by default
// - annotations
// - 3d objects / PDF3D
// - author / title metadata
// - first page / zoom settings metadata
// Notable exceptions/omissions:
// - javascript scripts and actions

// This script can also serve as an example on how to change any of these
// settings manually, or copy them differently.

function copyPage(dstDoc, srcDoc, pageNumber, dstFromSrc) {
    var srcPage, dstPage
    srcPage = srcDoc.findPage(pageNumber)
    dstPage = dstDoc.newDictionary()
    dstPage.Type = dstDoc.newName("Page")
    if (srcPage.MediaBox) dstPage.MediaBox = dstFromSrc.graftObject(srcPage.MediaBox)
    if (srcPage.Rotate) dstPage.Rotate = dstFromSrc.graftObject(srcPage.Rotate)
    if (srcPage.Resources) dstPage.Resources = dstFromSrc.graftObject(srcPage.Resources)
    if (srcPage.Contents) dstPage.Contents = dstFromSrc.graftObject(srcPage.Contents)
    if (srcPage.Group) dstPage.Group = dstFromSrc.graftObject(srcPage.Group)
    if (srcPage.Annots) dstPage.Annots = dstFromSrc.graftObject(srcPage.Annots)
    dstDoc.insertPage(-1, dstDoc.addObject(dstPage))
}

function copyAllPages(dstDoc, srcDoc) {
    var dstFromSrc = dstDoc.newGraftMap()
    var k, n = srcDoc.countPages()
    for (k = 0; k < n; ++k)
        copyPage(dstDoc, srcDoc, k, dstFromSrc)
}

function copyOutlineRec(cursor, srcDoc, startPage, list) {
    list.forEach(function (node) {
        // Rewrite link destination URI, to increment the "page" parameter
        var uri = node.uri
        if (uri.slice(0, 6) == "#page=") {
            var amp = uri.search("&")
            if (amp == -1) amp = uri.length
            var page = Number(uri.slice(6, amp))
            var rest = uri.slice(amp)
            uri = "#page=" + (startPage + page) + rest
        }

        // Insert empty item, to insert its children first
        cursor.insert({})
        cursor.prev()
        if (node.down) {
            cursor.down()
            copyOutlineRec(cursor, srcDoc, startPage, node.down)
            cursor.up()
        }

        // Add information to item afterwards, so we can set its open status
        cursor.update({ title: node.title, uri: uri, open: node.open })
        cursor.next()
    })
}

function copyOutline(dstDoc, srcDoc, startPage) {
    var cursor = dstDoc.outlineIterator()
    while (cursor.item())
        cursor.next()
    copyOutlineRec(cursor, srcDoc, startPage, srcDoc.loadOutline())
}

function copyMeta(dstDoc, srcDoc) {
    var dstRoot = dstDoc.getTrailer().Root
    var srcRoot = srcDoc.getTrailer().Root
    var dstInfo = dstDoc.getTrailer().Info
    var srcInfo = srcDoc.getTrailer().Info

    // Use the metadata items found in the most recent pdf file
    if (srcRoot.PageLayout) dstRoot.PageLayout = srcRoot.PageLayout
    if (srcRoot.PageMode) dstRoot.PageMode = srcRoot.PageMode
    if (srcInfo.Title) dstInfo.Title = srcInfo.Title
    if (srcInfo.Author) dstInfo.Author = srcInfo.Author
    if (srcInfo.Subject) dstInfo.Subject = srcInfo.Subject
    if (srcInfo.Keywords) dstInfo.Keywords = srcInfo.Keywords
}

function pdfmerge() {
    var srcDoc, dstDoc, i

    // Initialize PDF and set version
    dstDoc = new PDFDocument()
    dstDoc.getTrailer().Root.Version = "1.4"
    dstDoc.getTrailer().Info = dstDoc.addObject({})

    var pages = 0
    for (i = 1; i < scriptArgs.length; ++i) {
        srcDoc = new PDFDocument(scriptArgs[i])
        copyAllPages(dstDoc, srcDoc)
        copyOutline(dstDoc, srcDoc, pages)
        copyMeta(dstDoc, srcDoc)
        pages += srcDoc.countPages()
    }

    // Set static metadata
    var dstInfo = dstDoc.getTrailer().Info
    dstInfo.Creator = dstDoc.newString("pdf-full-merge.js")
    dstInfo.Producer = dstDoc.newString("MuPDF")
    dstInfo.CreationDate = dstDoc.newString(
        "D:" + new Date().toISOString().replace(/[-:T]/g,"").split(".")[0])

    dstDoc.save(scriptArgs[0], "compress,garbage")
}

if (scriptArgs.length < 2)
    print("usage: mutool run pdf-full-merge.js output.pdf input1.pdf input2.pdf ...")
else
    pdfmerge()