Very specific utility for my workflow with Kyocera MFU, it reorders the pages of a two-sided document scanned from two sides in two batches. MFU creates PDF with pages for example 1,2,3,6,5,4 and the utility reorders them to 1,2,3,4,5,6. The example of manipulating PDF in native Go without external utilities.

pdf2slides.go

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"path"
	"path/filepath"
	"strings"

	pdf "github.com/pdfcpu/pdfcpu/pkg/api"
)

func main() {
	if len(os.Args) < 3 {
		os.Exit(1)
	}
	in := os.Args[1]
	out := os.Args[2]

	var (
		tmp string
		err error
	)
	var pcount int
	if pcount, err = pdf.PageCount(in); err != nil {
		fmt.Printf("%v\n", err)
	}
	if pcount < 1 {
		fmt.Printf("error: document has %d pages\n", pcount)
		os.Exit(1)
	}

	tmp, err = ioutil.TempDir("", "pdf2sides-")
	if err != nil {
		os.Exit(1)
	}
	defer os.RemoveAll(tmp)

	// Create single page PDFs for in.pdf in outDir using the default configuration.
	pdf.SplitFile(in, tmp, 1, nil)

	var (
		ext     = filepath.Ext(in)
		base    = filepath.Base(strings.TrimRight(in, ext))
		infiles []string
	)
	for p := 1; p <= pcount/2; p++ {
		lname := path.Join(tmp, fmt.Sprintf("%s_%d%s", base, p, ext))
		infiles = append(infiles, lname)
		if pcount-p+1 == p {
			break
		}
		rname := path.Join(tmp, fmt.Sprintf("%s_%d%s", base, pcount-p+1, ext))
		infiles = append(infiles, rname)
	}
	if err = pdf.MergeFile(infiles, out, nil); err != nil {
		fmt.Printf("%v\n", err)
	}
}