How to Add Page Numbers to a PDF — Free Online Tool and Code Guide

import { PDFDocument, rgb, StandardFonts } from 'pdf-lib';
import fs from 'fs';
 
async function addPageNumbers(inputPath, outputPath, options = {}) {
  const {
    position = 'bottom-center',
    format = 'page-n',       // 'n', 'page-n', 'n-of-total', 'dash-n-dash'
    startNumber = 1,
    fontSize = 12,
    color = rgb(0.3, 0.3, 0.3),
    margin = 30,
  } = options;
 
  const existingPdfBytes = fs.readFileSync(inputPath);
  const pdfDoc = await PDFDocument.load(existingPdfBytes);
  const font = await pdfDoc.embedFont(StandardFonts.Helvetica);
  const pages = pdfDoc.getPages();
  const totalPages = pages.length;
 
  pages.forEach((page, index) => {
    const { width, height } = page.getSize();
    const pageNumber = startNumber + index;
 
    let label;
    switch (format) {
      case 'n':            label = `${pageNumber}`; break;
      case 'page-n':       label = `Page ${pageNumber}`; break;
      case 'n-of-total':   label = `${pageNumber} of ${totalPages}`; break;
      case 'dash-n-dash':  label = `- ${pageNumber} -`; break;
      default:             label = `${pageNumber}`;
    }
 
    const textWidth = font.widthOfTextAtSize(label, fontSize);
 
    let x, y;
    switch (position) {
      case 'bottom-center': x = (width - textWidth) / 2; y = margin; break;
      case 'bottom-left':   x = margin; y = margin; break;
      case 'bottom-right':  x = width - textWidth - margin; y = margin; break;
      case 'top-center':    x = (width - textWidth) / 2; y = height - margin; break;
      case 'top-left':      x = margin; y = height - margin; break;
      case 'top-right':     x = width - textWidth - margin; y = height - margin; break;
      default:              x = (width - textWidth) / 2; y = margin;
    }
 
    page.drawText(label, { x, y, size: fontSize, font, color });
  });
 
  const pdfBytes = await pdfDoc.save();
  fs.writeFileSync(outputPath, pdfBytes);
  console.log(`Added page numbers to ${totalPages} pages → ${outputPath}`);
}
 
// Usage
await addPageNumbers('input.pdf', 'output.pdf', {
  position: 'bottom-center',
  format: 'n-of-total',
  startNumber: 1,
  fontSize: 11,
});

from pypdf import PdfReader, PdfWriter
from pypdf.generic import (
    NameObject, NumberObject, ArrayObject, StringObject
)
import io
 
# pypdf can copy pages and modify them, but for drawing text
# you need reportlab as a companion library
 
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter
from pypdf import PdfReader, PdfWriter
 
def create_page_number_overlay(width, height, text, font_size=12, position='bottom-center'):
    packet = io.BytesIO()
    c = canvas.Canvas(packet, pagesize=(width, height))
    c.setFont("Helvetica", font_size)
    
    text_width = c.stringWidth(text, "Helvetica", font_size)
    margin = 30
    
    if position == 'bottom-center':
        x, y = (width - text_width) / 2, margin
    elif position == 'bottom-right':
        x, y = width - text_width - margin, margin
    elif position == 'bottom-left':
        x, y = margin, margin
    elif position == 'top-center':
        x, y = (width - text_width) / 2, height - margin
    elif position == 'top-right':
        x, y = width - text_width - margin, height - margin
    elif position == 'top-left':
        x, y = margin, height - margin
    else:
        x, y = (width - text_width) / 2, margin
    
    c.setFillColorRGB(0.3, 0.3, 0.3)
    c.drawString(x, y, text)
    c.save()
    packet.seek(0)
    return PdfReader(packet)
 
def add_page_numbers(input_path, output_path, 
                     position='bottom-center', 
                     fmt='page-n',
                     start=1):
    reader = PdfReader(input_path)
    writer = PdfWriter()
    total = len(reader.pages)
 
    for i, page in enumerate(reader.pages):
        page_num = start + i
        w = float(page.mediabox.width)
        h = float(page.mediabox.height)
 
        if fmt == 'n':            label = str(page_num)
        elif fmt == 'page-n':     label = f"Page {page_num}"
        elif fmt == 'n-of-total': label = f"{page_num} of {total}"
        elif fmt == 'dash-n':     label = f"- {page_num} -"
        else:                     label = str(page_num)
 
        overlay = create_page_number_overlay(w, h, label, position=position)
        page.merge_page(overlay.pages[0])
        writer.add_page(page)
 
    with open(output_path, 'wb') as f:
        writer.write(f)
    print(f"Done: {total} pages numbered → {output_path}")
 
# Usage
add_page_numbers('input.pdf', 'numbered.pdf',
                 position='bottom-center',
                 fmt='n-of-total',
                 start=1)

# Using Ghostscript to add page numbers
gs -dBATCH -dNOPAUSE -sDEVICE=pdfwrite \
   -sOutputFile=output.pdf \
   -c "<<
     /EndPage {
       2 eq { pop false } {
         gsave
         /Helvetica findfont 12 scalefont setfont
         0.3 0.3 0.3 setrgbcolor
         currentpage /PageCount get 1 add dup
         exch (Page ) exch
         10 string cvs concatstrings
         297 20 moveto
         show
         grestore true
       } ifelse
     }
   >> setpagedevice" \
   -f input.pdf

// pdf-lib: start counting at page 2, first page gets no number
pages.forEach((page, index) => {
  if (index === 0) return; // skip cover
  const pageNumber = startNumber + index - 1; // adjust count
  // ... draw the number
});

pages.forEach((page, index) => {
  // Number only pages 3–15 (index 2–14)
  if (index < 2 || index > 14) return;
  const pageNumber = startNumber + (index - 2);
  // ... draw the number
});

pages.forEach((page, index) => {
  const { width, height } = page.getSize();
  const pageNumber = startNumber + index;
  const label = `${pageNumber}`;
  const textWidth = font.widthOfTextAtSize(label, fontSize);
  
  // Even pages: left edge; odd pages: right edge
  const isEven = (index + 1) % 2 === 0;
  const x = isEven ? margin : width - textWidth - margin;
  const y = margin;
  
  page.drawText(label, { x, y, size: fontSize, font, color });
});