GoPDF

A Go library for reading PDF files, with active CJK text extraction support.

Requires Go 1.25+ (go.mod directive).

Originally forked from ledongthuc/pdf; now an independent project. Original lineage: rsc/pdf.

Features

• Plain text extraction with context/cancellation support
• Styled text extraction (font name, size, position)
• Text grouped by row
• Pages() iter.Seq2[int, Page] and Texts() iter.Seq[Text] — lazy iterators for streaming access (Go 1.23+)
• OpenBytes([]byte) — parse a PDF from an in-memory byte slice
• Page.MediaBox() and Page.CropBox() — page dimensions with inheritance-chain resolution
• Document metadata API (r.Info(): title, author, dates, …)
• Outline (table of contents) with resolved page numbers
• Encrypted PDF support — transparent decryption of Standard-security-handler files: RC4 (40/128-bit, V=1/2), AES-128 (V=4, AESV2), and AES-256 (V=5, R=5/R=6 — Acrobat 9+ and PDF 2.0 / ISO 32000-2). Open with the empty, user, or owner password via NewReaderEncrypted.
• CJK predefined CMap decoders:
  • Japanese Shift-JIS (90ms-RKSJ-H/V, 90pv-RKSJ-H)
  • CJK UCS-2 BE (UniGB-UCS2-H/V, UniCNS-UCS2-H/V, UniJIS-UCS2-H/V, UniKS-UCS2-H/V)
  • Simplified Chinese GBK / GB-EUC / GBKp-EUC (GBK-EUC-H/V, GB-EUC-H/V, GBKp-EUC-H/V)
  • Traditional Chinese Big5-ETen / ETenms (ETen-B5-H/V, ETenms-B5-H/V)
  • Korean UHC / KSC-EUC / UHC-HW (KSCms-UHC-H/V, KSC-EUC-H/V, KSCms-UHC-HW-H/V)

Install

go get github.com/Detective-XH/gopdf

Examples

See the examples/ folder for runnable programs.

Read plain text

package main

import (
	"bytes"
	"context"
	"fmt"

	"github.com/Detective-XH/gopdf"
)

func main() {
	f, r, err := pdf.Open("./sample.pdf")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	var buf bytes.Buffer
	b, err := r.GetPlainText(context.Background())
	if err != nil {
		panic(err)
	}
	buf.ReadFrom(b)
	fmt.Println(buf.String())
}

Read styled text

package main

import (
	"context"
	"fmt"

	"github.com/Detective-XH/gopdf"
)

func main() {
	f, r, err := pdf.Open("./sample.pdf")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	sentences, err := r.GetStyledTexts(context.Background())
	if err != nil {
		panic(err)
	}
	for _, s := range sentences {
		fmt.Printf("font=%s size=%.1f x=%.1f y=%.1f text=%s\n",
			s.Font, s.FontSize, s.X, s.Y, s.S)
	}
}

Read text by row

package main

import (
	"fmt"
	"os"

	"github.com/Detective-XH/gopdf"
)

func main() {
	f, r, err := pdf.Open(os.Args[1])
	if err != nil {
		panic(err)
	}
	defer f.Close()

	for i := 1; i <= r.NumPage(); i++ {
		p := r.Page(i)
		if p.V.IsNull() {
			continue
		}
		rows, _ := p.GetTextByRow()
		for _, row := range rows {
			fmt.Printf("row %d:", row.Position)
			for _, word := range row.Content {
				fmt.Printf(" %s", word.S)
			}
			fmt.Println()
		}
	}
}

Limitations

• Text extraction only — no PDF creation, modification, or rendering.
• Image content is not decoded (location metadata via Page.Images() is planned).
• No AcroForms extraction yet (planned).
• Requires Go 1.23+ for Pages() / Texts() iterators; all other APIs work on Go 1.21+.

Changelog

See CHANGELOG.md for the full history of fixes and additions.