pages/pdf_merge.go

/*
 * Basic merging of PDF files.
 * Simply loads all pages for each file and writes to the output file.
 * See pdf_merge_advanced.go for a more advanced version which handles merging document forms (acro forms) also.
 *
 * Run as: go run pdf_merge.go output.pdf input1.pdf input2.pdf input3.pdf ...
 */

package main

import (
	"errors"
	"fmt"
	"os"

	unicommon "github.com/unidoc/unipdf/v3/common"
	pdf "github.com/unidoc/unipdf/v3/model"
)

func init() {
	// Debug log level.
	unicommon.SetLogger(unicommon.NewConsoleLogger(unicommon.LogLevelDebug))
}

func main() {
	if len(os.Args) < 4 {
		fmt.Printf("Requires at least 3 arguments: output_path and 2 input paths\n")
		fmt.Printf("Usage: go run pdf_merge.go output.pdf input1.pdf input2.pdf input3.pdf ...\n")
		os.Exit(0)
	}

	outputPath := ""
	inputPaths := []string{}

	// Sanity check the input arguments.
	for i, arg := range os.Args {
		if i == 0 {
			continue
		} else if i == 1 {
			outputPath = arg
			continue
		}

		inputPaths = append(inputPaths, arg)
	}

	err := mergePdf(inputPaths, outputPath)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Complete, see output file: %s\n", outputPath)
}

func mergePdf(inputPaths []string, outputPath string) error {
	pdfWriter := pdf.NewPdfWriter()

	for _, inputPath := range inputPaths {
		f, err := os.Open(inputPath)
		if err != nil {
			return err
		}

		defer f.Close()

		pdfReader, err := pdf.NewPdfReader(f)
		if err != nil {
			return err
		}

		isEncrypted, err := pdfReader.IsEncrypted()
		if err != nil {
			return err
		}

		if isEncrypted {
			auth, err := pdfReader.Decrypt([]byte(""))
			if err != nil {
				return err
			}
			if !auth {
				return errors.New("Cannot merge encrypted, password protected document")
			}
		}

		numPages, err := pdfReader.GetNumPages()
		if err != nil {
			return err
		}

		for i := 0; i < numPages; i++ {
			pageNum := i + 1

			page, err := pdfReader.GetPage(pageNum)
			if err != nil {
				return err
			}

			err = pdfWriter.AddPage(page)
			if err != nil {
				return err
			}
		}
	}

	fWrite, err := os.Create(outputPath)
	if err != nil {
		return err
	}

	defer fWrite.Close()

	err = pdfWriter.Write(fWrite)
	if err != nil {
		return err
	}

	return nil
}