Merge PDF Files Free (Online and Offline Methods)

You've got three PDFs that should be one. Maybe it's chapters of a report, pages of a contract, or a collection of invoices. Whatever the reason, merging PDFs is a common task, and there are plenty of free ways to do it.

Let's go through the options, starting with what you probably already have installed.

Method 1: macOS Preview (Built-in, Free)

If you're on a Mac, you already have a PDF merger. Preview can combine PDFs without any extra software.

1. Open the first PDF you want to merge in Preview (the default app)
2. Open the other PDFs you want to merge — each in its own Preview window
3. In the first PDF, open the sidebar (View → Thumbnails)
4. For each additional PDF:
   • Click on a page in that PDF's sidebar
   • Press Cmd+A to select all pages
   • Drag them into the first PDF's sidebar
5. Drag the pages around to reorder them as needed
6. File → Export as PDF to save the merged file

Tip: You can also drag individual pages instead of selecting all. This lets you pick and choose which pages to include from each PDF.

Pros: Free, built into macOS, no upload needed, works offline, handles reordering

Cons: Mac-only, manual process (no batch automation)

Method 2: Adobe Acrobat (Paid, Most Features)

If you have Adobe Acrobat Pro, merging PDFs is straightforward and powerful.

1. Open Adobe Acrobat
2. Tools → "Combine Files"
3. Click "Add Files" or drag and drop your PDFs
4. Reorder the files (and individual pages within files) as needed
5. Choose "Combine Files" or "Merge Files" (similar, but with slightly different options)
6. Save the merged PDF

Adobe lets you:

• Merge entire files or select specific pages from each
• Reorder files and pages with drag-and-drop
• Set the order in which files are merged
• Choose whether to merge page sizes or use a uniform size
• Add bookmarks or headers/footers during the merge

Pros: Most feature-rich, handles complex merges, integrates with other Adobe tools

Cons: Paid ($20+/month), overkill for simple merges

Method 3: Online Mergers (Free-ish, Privacy Trade-off)

There are dozens of websites that merge PDFs for free. Popular options include iLovePDF, Smallpdf, PDF2Go, ILovePDF, and MergePDF.io.

1. Go to the merger's website
2. Drag and drop your PDFs or click to upload
3. Reorder the files (most sites let you do this)
4. Click "Merge" or "Combine"
5. Wait for processing
6. Download the merged PDF

Most online mergers offer:

• Drag-and-drop file uploads
• File reordering with click-and-drag
• Selection of specific pages from each file
• Quick processing (usually a few seconds)
• Free tiers with daily usage limits

Pros: Easy to use, no software installation, works on any device with a browser, often faster than desktop software

Cons: Upload your files to third-party servers, may have file size limits, daily usage limits on free tiers, privacy concerns

Privacy warning: If your PDFs contain sensitive information (financial documents, personal data, contracts), think twice before uploading them. Most sites claim to delete files after a short period (hours to days), but during that window, your data is on their servers.

Method 4: Google Chrome (Free, Works Locally)

Chrome has a built-in PDF viewer, but it doesn't have a merge feature. However, there's a Chrome extension approach:

Using Chrome Extensions

Extensions like "PDF Mergy" and "Merge PDF" add merge functionality to Chrome. These run locally in your browser, so your files aren't uploaded anywhere.

1. Open the Chrome Web Store
2. Search for "merge PDF" or "PDF merge"
3. Choose a well-reviewed extension
4. Add it to Chrome
5. Click the extension icon → select your PDFs
6. Reorder as needed → merge → download

Pros: Free, no software installation, runs locally (no upload), works in your browser

Cons: Requires Chrome, extension quality varies, some extensions may have ads or permissions concerns

Method 5: Command Line Tools (Free, Tech-Savvy)

For developers, terminal users, or anyone automating PDF workflows, command-line tools are powerful and scriptable.

Using qpdf (Linux/Mac/Windows)

QPDF is a command-line PDF manipulation library that can merge files.

Install on Ubuntu/Debian:

sudo apt install qpdf

Install on Mac:

brew install qpdf

Merge multiple PDFs:

qpdf --empty --pages file1.pdf file2.pdf file3.pdf -- output.pdf

This creates an empty PDF and fills it with all pages from the three files, in order.

Using pdftk (Linux/Mac/Windows)

PDFtk is another powerful command-line PDF tool.

Install on Ubuntu/Debian:

sudo apt install pdftk

Merge PDFs:

pdftk file1.pdf file2.pdf file3.pdf cat output output.pdf

Using Ghostscript

Ghostscript is a PostScript/PDF interpreter that can merge files.

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=output.pdf file1.pdf file2.pdf file3.pdf

Pros: Free, scriptable, no GUI overhead, works in automation pipelines, no privacy concerns (local processing)

Cons: Requires command-line knowledge, steeper learning curve, need to install dependencies

Method 6: PDFsam (Free, Open Source, Desktop)

PDFsam (PDF Split and Merge) is a free, open-source desktop application dedicated to splitting and merging PDFs. It has both a basic free version and a paid enhanced version.

PDF Basic (Free)

The free version handles merging, splitting, and rotating PDFs.

1. Download PDFsam from pdfsam.org
2. Open the application
3. Click "Merge"
4. Drag and drop your PDFs
5. Reorder as needed
6. Choose output settings (filename, location)
7. Click "Run" to merge

PDFsam Basic is available for Windows, Mac, and Linux.

Pros: Free, open source, cross-platform, dedicated tool (does one thing well), no privacy concerns

Cons: Requires software installation, fewer features than Adobe

Merging Specific Pages Only

Sometimes you don't want to merge entire files — you want specific pages from each. Most tools handle this:

Online Mergers

Most let you expand each file and select or deselect individual pages before merging.

Adobe Acrobat

Click the file to expand it, then select the pages you want to include.

Command Line (qpdf)

To merge pages 1-5 from file1.pdf and all of file2.pdf:

qpdf --empty --pages file1.pdf 1-5 file2.pdf -- output.pdf

macOS Preview

Just select the specific pages you want from each file and drag them into the main PDF.

Reordering Pages During Merge

The order you upload/select files becomes the order of pages in the merged PDF. Most tools let you reorder:

Online Mergers

Drag files up and down to reorder them in the list.

Adobe Acrobat

Click the arrows next to file thumbnails to reorder, or drag them to new positions.

macOS Preview

After dragging all pages into one sidebar, drag individual pages to reorder them.

Common Problems and Fixes

Problem: Merged PDF Has Inconsistent Page Sizes

Cause: The original PDFs had different page sizes (A4, Letter, custom sizes). When merged, these differences become obvious.

Fix: Most merge tools have an option to normalize page sizes. In Adobe Acrobat, you can choose "Make all pages the same size" before merging. Alternatively, resize individual files before merging using a PDF editor.

Problem: Bookmarks Are Lost in the Merged PDF

Cause: Bookmarks don't always carry over during merges, especially with online tools.

Fix: Use Adobe Acrobat or PDFsam, which handle bookmarks better. Alternatively, create new bookmarks after merging in your PDF reader.

Problem: Fonts Look Different After Merge

Cause: Embedded fonts in the original PDFs may not transfer perfectly during the merge process.

Fix: This is hard to fix after the fact. The best approach is to ensure all source PDFs use similar fonts, or use Adobe Acrobat which does a better job preserving font information.

Problem: Large File Size After Merge

Cause: Merging doesn't compress — it just combines files. The result is the sum of the original sizes, plus some overhead.

Fix: Compress the merged PDF after merging. There are free online compressors and built-in tools in Adobe Acrobat that can reduce file size significantly.

Batch Merging: Automating the Process

If you regularly merge PDFs (e.g., daily reports, monthly invoices), automating the process saves time.

Command Line Scripts

Write a shell script that uses qpdf or pdftk:

#!/bin/bash qpdf --empty --pages file1.pdf file2.pdf file3.pdf -- "$(date +%Y-%m-%d)-merged.pdf"

This creates a dated merged PDF. Add it to your crontab or task scheduler to run automatically.

Python with PyPDF2

For more flexibility, use Python's PyPDF2 library:

from PyPDF2 import PdfMerger merger = PdfMerger() merger.append("file1.pdf") merger.append("file2.pdf") merger.append("file3.pdf") merger.write("merged.pdf") merger.close()

Desktop Automation Tools

On Mac, Automator or Hazel can watch a folder for new PDFs and automatically merge them. On Windows, Power Automate or Task Scheduler can do similar work.

Quick Reference: Which Method Should You Use?

"I'm on a Mac"

• Preview (built-in, free)

"I'm on Windows, don't have Adobe"

• Online merger (convenient, uploads files)
• PDFsam (free desktop app)
• Chrome extension (runs locally)

"I have Adobe Acrobat"

• Adobe Acrobat's Combine Files feature

"I'm comfortable with the command line"

• qpdf or pdftk (fast, scriptable)

"Privacy is important — I can't upload my files"

• Preview (Mac)
• Adobe Acrobat
• PDFsam
• Command-line tools

"I need to merge files regularly"

• Set up automation with scripts or desktop tools
• Adobe Acrobat for complex workflows

The Bottom Line

Merging PDFs is straightforward once you pick the right tool. Preview on Mac is the best free option for Mac users. Online mergers are the most convenient for occasional use. Adobe Acrobat offers the most features for power users. And command-line tools are perfect for automation.

If privacy matters, stick to local tools (Preview, Adobe, PDFsam, command line). If convenience matters, online mergers get the job done quickly. And if you're doing this regularly, consider automating the process to save time.