The fastest way to combine PDFs depends on what you already have

You can combine two PDF documents using free tools built into Windows or macOS, or using a dedicated PDF tool if you need to do this regularly. The simplest route is usually your operating system — Windows has a print-to-PDF feature, and macOS has Preview. If you work with PDFs often, a dedicated tool like Adobe Acrobat Reader (free version), ILovePDF, or Smallpdf will be faster once you learn where the button is.

The method you choose depends on whether you're combining two files once or dozens of times. A one-time job takes five minutes with your operating system. Repeated jobs are worth learning a dedicated tool for, because you'll spend less time hunting for the feature each time.

Key Takeaways

  • Windows and macOS both have built-in ways to combine PDFs without installing anything new — use Print to PDF on Windows or drag files into Preview on macOS.
  • Dedicated PDF tools like Adobe Acrobat Reader, ILovePDF, and Smallpdf have a combine or merge button that's always in the same place, making them faster for repeated work.
  • The order of your pages matters — most tools let you drag pages around before you save, so check the preview before you finish.
  • Your combined file will be larger than either original file, so make sure you have enough storage space before you start.

Combining PDFs on Windows using Print to PDF

Open the first PDF in any program that can read PDFs — Adobe Reader, Microsoft Edge, or even File Explorer will work. Go to File, then Print. In the printer dropdown, select "Print to PDF" or "Microsoft Print to PDF" depending on your Windows version. Click Print, choose where to save the new file, and name it something you'll recognize.

Now open the second PDF in the same program. Print it the same way, but this time select "Append to the existing PDF" if that option appears, or print it to a temporary file with a different name. If you printed to a temporary file, you now have three PDFs: the original two plus a new one with just the second document. You'll need to use a dedicated PDF tool to combine all three into one final file.

This method works but is clunky for more than two documents. If you're combining more than two files, skip to the dedicated tools section below.

Combining PDFs on macOS using Preview

Open the first PDF in Preview — you can do this by right-clicking the file, selecting "Open With," and choosing Preview. Once it's open, go to File and select "Open" again. Find the second PDF and open it. Preview will open it in a new window.

Now you have two Preview windows open. In the window with the second PDF, select all pages (Command+A), then copy them (Command+C). Switch to the first PDF window, go to Edit, and select "Paste." The pages from the second PDF will be added to the end of the first one. Go to File and select "Export as PDF" to save your combined document with a new name.

If the pages are in the wrong order, you can rearrange them before you export. In the sidebar on the left, you'll see thumbnails of all your pages. Click and drag them to reorder them, then export.

Using Adobe Acrobat Reader to combine PDFs

Adobe Acrobat Reader is free and has a dedicated Combine Files tool. Open Adobe Acrobat Reader, go to Tools (in the top menu or left sidebar depending on your version), and look for "Combine Files" or "Merge PDFs." Click it.

A window will open asking you to add files. Click "Add Files" and select both PDFs you want to combine. The tool will show you a preview of the pages in order. If they're in the wrong order, click and drag the file names or page thumbnails to rearrange them. Once you're satisfied, click "Combine" or "Merge," choose where to save, and you're done.

This method is reliable and the same every time, which makes it worth learning if you combine PDFs more than once a month.

Using free online tools like ILovePDF or Smallpdf

Go to ILovePDF.com or Smallpdf.com in your web browser. Look for a button that says "Merge PDF" or "Combine PDF." Click it. You'll see an area where you can drag and drop files or click to browse your computer. Select both PDFs you want to combine.

The tool will show you a preview of the pages in the order they'll be combined. Most tools let you drag pages around to reorder them before you finish. Once the order is correct, click "Merge" or "Combine," and the tool will create a new file and read it to your computer.

These tools work in any web browser and don't require installation. The trade-off is that you're uploading your files to someone else's server. If your PDFs contain sensitive information, use the Windows, macOS, or Adobe methods instead, which keep your files on your own computer.

Checking your combined file and fixing common problems

After you combine your PDFs, open the new file and scroll through it to make sure all pages are there and in the right order. If pages are missing or out of order, you'll need to redo the combination — most tools don't have an undo button once you've saved.

If your combined file is much larger than you expected, it may contain high-resolution images or embedded fonts. This is normal and usually not a problem unless you're trying to email the file. If file size is an issue, you can use a compression tool, but this may reduce image quality.

If one of your original PDFs was password-protected, you may not be able to combine it without entering the password first. Open the protected PDF in Adobe Reader or your web browser, enter the password, and save it as a new unprotected copy before combining.

When to use each method

Use your operating system's built-in tools (Print to PDF on Windows, Preview on macOS) if you're combining two PDFs once and want the fastest setup. You don't need to install anything, and the process takes about five minutes total.

Use Adobe Acrobat Reader if you combine PDFs regularly — the Combine Files tool is always in the same place, and you can reorder pages before saving. It's free and works on both Windows and macOS.

Use an online tool like ILovePDF or Smallpdf if you don't want to install software or if you're working on a computer where you can't install programs. Remember that your files will be uploaded to their servers, so don't use this method for confidential documents.

Frequently Asked Questions

Can I combine more than two PDFs at once?

Yes. Adobe Acrobat Reader, ILovePDF, and Smallpdf all let you add three or more files at once. Your operating system's built-in tools are slower for this — you'd have to combine two files, then combine that result with a third, which takes multiple steps.

Will combining PDFs change the quality of the images inside?

No, combining PDFs does not reduce image quality. The images stay exactly as they were in the original files. The combined file will be larger because it contains all the data from both originals, but the quality remains the same.

What if the pages are in the wrong order after I combine them?

Most tools show you a preview with page thumbnails before you save. You can click and drag the pages or files to reorder them. If you already saved the file in the wrong order, you'll need to redo the combination — there's no way to rearrange pages after saving in most free tools.

Can I combine a PDF with a Word document or image file?

No, PDF combination tools only work with PDF files. If you need to combine a Word document with a PDF, convert the Word document to PDF first using File > Export as PDF in Microsoft Word, then combine the two PDFs.

Is it safe to use online PDF tools with confidential documents?

Online tools upload your files to their servers, which means your documents leave your computer. If your PDFs contain sensitive information, use Adobe Acrobat Reader or your operating system's built-in tools instead, which keep everything on your own computer.