2026-05-09 · 7 min read

How to Merge Multiple PDFs Into One File

Merging PDFs is one of the most-Googled PDF tasks. Eleven receipts for an expense claim, a portfolio of work samples for an application, a signed contract plus the addendum plus the schedule — at some point every office worker has needed to combine PDFs into a single file. The good news: it’s a fast, lossless operation, and you don’t need Adobe to do it. Here are five ways, ranked by ease.

Method 1 — Browser-based merger (fastest)

For most people, a browser-based merger is the path of least resistance: drag in your files, reorder by clicking, hit merge, get a single PDF. No installs, no account. The only question is whether the tool runs on-device or uploads your files to a server. For anything sensitive — payslips, tax documents, IDs — pick one that runs locally. Our PDF merge tool does the merge entirely in your browser; nothing is uploaded.

Merging is faster than most other PDF tasks because it doesn’t require re-encoding the page content. The tool just rewrites the PDF document tree to point at all the input pages in order. A 200-page merge can finish in under a second.

Method 2 — macOS Preview

If you’re on a Mac, you almost never need a third-party tool. Preview’s thumbnail sidebar handles merging beautifully:

1. Open the first PDF in Preview.
2. Show thumbnails: View → Thumbnails (or Cmd-Option-2).
3. Drag the additional PDFs into the sidebar — drop them between thumbnails to position pages where you want them.
4. File → Export as PDF, give it a new name.

One subtle thing: dragging a PDF onto an existing page (rather than between pages) can cause Preview to merge the documents at that point rather than appending. If you get unexpected ordering, it’s usually because of a misplaced drop.

Method 3 — Windows: PDF24, PDFsam, or Edge

Windows doesn’t have a built-in PDF merger as elegant as Preview’s, but two free desktop apps fill the gap:

• PDF24 Creator — free, ad-free, works offline, has a nice drag-and-drop merge UI.
• PDFsam Basic — open-source, focused, supports merging and splitting from the same interface.

Microsoft Edge also has rudimentary print-to-PDF based combining: open each PDF, print to PDF, repeat. Slow and lossy because it re-rasterises — fine for small files, painful at any scale.

Method 4 — Command line (best for many files or scripting)

For batch jobs, scheduled merges, or merging dozens of files, command line wins. The two best free tools:

# qpdf — fast, preserves bookmarks
qpdf --empty --pages a.pdf b.pdf c.pdf -- merged.pdf

# pdftk — slightly simpler syntax
pdftk a.pdf b.pdf c.pdf cat output merged.pdf

# Wildcards work too
qpdf --empty --pages *.pdf -- merged.pdf

# Specific page ranges
qpdf --empty --pages a.pdf 1-5 b.pdf 10-z -- merged.pdf

Command-line tools are also the only way to get a single command in a Makefile, GitHub Action, or shell script. If you find yourself merging the same files weekly, this is the move.

Method 5 — Programmatic merging (Python, JavaScript)

If your merge is part of a larger pipeline (generating reports, assembling invoices), you probably want a library:

# Python with pypdf
from pypdf import PdfWriter
writer = PdfWriter()
for f in ["intro.pdf", "body.pdf", "appendix.pdf"]:
    writer.append(f)
writer.write("output.pdf")

# Node.js with pdf-lib
import { PDFDocument } from "pdf-lib";
const out = await PDFDocument.create();
for (const path of files) {
  const doc = await PDFDocument.load(fs.readFileSync(path));
  const pages = await out.copyPages(doc, doc.getPageIndices());
  pages.forEach(p => out.addPage(p));
}
fs.writeFileSync("out.pdf", await out.save());

Things that can go wrong

A few gotchas worth knowing about before you merge:

• Mixed page sizes. If one PDF is A4 and another is US Letter, the merged file has both. Most viewers handle this fine, but if you need uniform sizing, normalise before merging — Preview can rescale via Print → Save as PDF.
• Bookmarks and links. Cheap mergers strip bookmarks and internal hyperlinks. If you care about navigation in long merged documents, use qpdf or pdftk; they preserve outline trees.
• Encrypted source files. You usually have to decrypt before merging. qpdf --decrypt --password=PW in.pdf out.pdf handles this.
• Form fields. Two PDFs with form fields named identically can collide; the second one’s values overwrite the first. Flatten forms before merging if this matters.
• File size. Merging is additive — your output is (roughly) the sum of inputs. If the result is too big to email, see our related guide for compression strategies.

Reordering, removing, or rotating pages while merging

Most good mergers let you do more than concatenate. After dropping in your files, you can typically:

• Drag thumbnails to reorder pages.
• Delete unwanted pages from the merge sequence.
• Rotate landscape pages to portrait or vice versa.
• Insert blank pages between sections.

These are the operations that turn a merge from “stack PDFs end to end” into “assemble a real document.” Worth the 30 seconds of extra clicks.

Quick decision matrix

Need it done now without installing anything? Drop your files into our browser-based PDF merger. Files never leave your device. Or if you started with a single PDF you need to convert before merging anything else, our PDF to Word converter is one click away.