PDF Merge

How to use

1. Select the PDFs in the order they should be merged.
2. Check each file's page count and the total.
3. Merge and download the combined file.
4. Remove open passwords first, and keep the batch and file sizes reasonable.

How it works

Select and merge

Press "choose files" to pick multiple PDFs at once (or append in batches); the page lists each file's name and page count. Press merge for a concatenated file in order, then download.

Order follows selection

Merging follows your selection order in the file picker. To change order, re-select the files in the target sequence; if a few are wrong, clearing and re-picking beats deleting one by one.

Password-protected PDFs

PDFs with an open password can't be read and so can't merge; remove the open password (not permission restrictions) locally first, then merge here.

No re-encoding, content intact

No. Merging moves pages as-is without re-encoding — text and images stay intact. New metadata is written, so a small size difference from the sum of the parts is normal.

Code example

import { PDFDocument } from 'pdf-lib';

// copyPages deep-copies pages into the target document, so merging is repeatable
async function mergePdfs(files) {
  const out = await PDFDocument.create();
  for (const file of files) {
    const src = await PDFDocument.load(await file.arrayBuffer());
    const pages = await out.copyPages(src, src.getPageIndices());
    pages.forEach((p) => out.addPage(p));
  }
  return out.save();               // Uint8Array, hand it straight to a Blob download
}
const bytes = await mergePdfs(fileInput.files);

from pypdf import PdfWriter

writer = PdfWriter()
for path in ['a.pdf', 'b.pdf', 'c.pdf']:
    writer.append(path)            # append adds every page; add_page picks them one by one

with open('merged.pdf', 'wb') as f:
    writer.write(f)

FAQ