How to Merge Two PDF Files Into One

The fastest way depends on what you have installed

You can merge two PDFs on Windows, Mac, or Linux without paying for software. The method that works fastest for you depends on whether you already have Adobe Reader, whether your operating system has a built-in tool, or whether you are willing to use a web browser.

On Windows 10 and 11, the Print to PDF feature built into the system can combine files if you print the first PDF, then print the second one to the same file — though this overwrites rather than merges. A better Windows approach is to use free software like PDFtk or Ghostscript, which run from the command line. On Mac, the Preview app (which opens automatically when you click a PDF) has a built-in merge function in the sidebar. On any system, a web-based PDF tool requires no installation but uploads your files to someone else's server.

The trade-off is between speed, privacy, and how much you want to learn. If you merge PDFs once a year, a web tool is fastest. If you do it weekly, installing free software on your computer saves time and keeps your files private.

Key Takeaways

Mac users can merge PDFs directly in the Preview app by dragging one file into the sidebar of another, then exporting as a new PDF.
Windows users without Adobe software can use free command-line tools like PDFtk or Ghostscript, or use a web-based PDF merger if they prefer not to install anything.
Web-based PDF mergers work on any device but upload your files to a third-party server, so avoid them if your PDFs contain sensitive information.
Adobe Acrobat Pro (paid software) has a dedicated merge tool in the menu, but free alternatives accomplish the same task without the cost.

Merging PDFs on Mac using Preview

The Preview app on Mac includes a merge function that takes about two minutes. Open the first PDF in Preview (double-click it, or right-click and select Open With > Preview). In the menu bar, click View, then select Thumbnails. A sidebar appears on the left showing pages from the first PDF as small images.

Open the second PDF in Finder. Drag it into the Preview window — either onto the sidebar or into the main document area. The pages from the second PDF appear in the sidebar below the first PDF's pages. You can reorder them by dragging thumbnails up or down. When the order is correct, go to File > Export As, choose a location and filename, and click Save. The merged PDF is now on your computer.

If you want to delete or rearrange pages before merging, right-click a thumbnail in the sidebar and select Delete Page. This removes it from the preview but does not change the original file.

Merging PDFs on Windows using free software

Windows does not have a built-in PDF merge tool in the way Mac does, but two free programs work well: PDFtk and Ghostscript. Both run from the command line, which means you type a command rather than clicking buttons. If you have never used the command line, this takes 10 to 15 minutes to learn; after that, merging takes 30 seconds.

To use PDFtk, read the installer from the PDFtk website, run it, and follow the setup steps. Open Command Prompt (search for "cmd" in the Windows search bar). Type the command: pdftk file1.pdf file2.pdf cat output merged.pdf — replacing file1.pdf and file2.pdf with your actual filenames. Press Enter. A new file called merged.pdf appears in the same folder. If your files are in a different folder, include the full path: pdftk C:\Users\YourName\Documents\file1.pdf C:\Users\YourName\Documents\file2.pdf cat output C:\Users\YourName\Documents\merged.pdf

Ghostscript works similarly but uses a longer command. Many people find PDFtk simpler for basic merging. Both are free and do not upload your files anywhere.

Merging PDFs using a web browser

If you do not want to install software, a web-based PDF tool works on any device. Go to a site like iLovePDF, SmallPDF, or PDF Merge (search for "merge PDF online"). Click the button to upload or drag your first PDF into the window. Then upload the second PDF. The tool shows thumbnails of both files. Drag them into the order you want, then click Merge or Combine. read the result to your computer.

The advantage is speed — no installation, no command line, works on phone or tablet. The disadvantage is that your PDFs are uploaded to someone else's server. If your PDFs contain bank statements, medical records, or other sensitive information, this is a privacy risk. Read the tool's privacy policy to see how long they keep files and whether they use them for other purposes.

Most web tools delete files after a few hours, but you have no way to verify this. For one-time merges of non-sensitive PDFs, web tools are practical. For regular use or sensitive documents, a tool installed on your own computer is safer.

Using Adobe Acrobat Pro if you already have it

If you subscribe to Adobe Acrobat Pro (the paid version, not the free Adobe Reader), merging is straightforward. Open Acrobat Pro, go to Tools, and select Combine Files. Click Add Files, select your two PDFs, and click Combine. Acrobat merges them in the order you selected and opens the result. Go to File > Save As to save it with a new name.

Adobe Acrobat Pro costs about $15 per month or $180 per year. It includes other tools like editing text within PDFs, adding signatures, and compressing file size. If you already pay for it, the merge function is included. If you do not have it, the free alternatives above accomplish the same task without the subscription.

Merging more than two PDFs

All the methods above work for three, four, or more PDFs — you straightforward add each file to the list instead of stopping at two. In Preview on Mac, drag as many PDFs as you want into the sidebar. In PDFtk on Windows, list all filenames in the command: pdftk file1.pdf file2.pdf file3.pdf file4.pdf cat output merged.pdf In web tools, click Add Files multiple times. The process is the same; it just takes a few seconds longer.

One thing to watch: if you are merging many large PDFs (each over 10 MB), the result can become slow to open or email. Most email services reject attachments over 25 MB. If your merged file is too large, you can compress it using the same tools — PDFtk and web mergers usually have a compress option — or split it back into smaller files.

Keeping the original files safe

All of these methods create a new file and leave your original PDFs unchanged. When you export from Preview, save from a web tool, or run a PDFtk command, you are creating a separate merged file. The originals stay where they were. This means you can experiment without worry — if the merge does not look right, you can try again without losing anything.

The one exception is if you delete pages from the Preview sidebar before exporting. That deletion only affects what Preview shows you; the original file is not changed. But to be safe, always check the merged result before deleting the originals from your computer.

Frequently Asked Questions

Can I merge PDFs on my phone or tablet?

Yes, using a web-based tool. Search for "merge PDF online" and use any of the sites mentioned above. Upload both files, arrange them, and read the result. Some phones have PDF apps with merge features — check your device's app store. The limitation is that phone screens are small, so reordering pages can be fiddly.

What if one PDF is much larger than the other?

File size does not affect merging. A 50 MB PDF and a 2 MB PDF merge just as easily as two 5 MB PDFs. The merged file will be roughly the sum of both sizes (50 + 2 = 52 MB in this example). If the result is too large to email, use a compression tool afterward.

Can I merge PDFs and rearrange the pages at the same time?

Yes. In Preview on Mac, drag thumbnails into any order before exporting. In web tools, the interface shows all pages and lets you drag them. In PDFtk, you can specify the order manually: pdftk file1.pdf file2.pdf file1.pdf cat output merged.pdf would put file1, then file2, then file1 again. This is useful if you want to repeat a page or put pages from different files in a custom order.

Does merging reduce the quality of the PDFs?

No. Merging straightforward combines the files without re-processing them. The quality stays the same. Compression tools can reduce quality if you choose to compress afterward, but merging alone does not.

What if the merge fails or looks wrong?

Try a different tool. If Preview fails on Mac, use a web tool. If a web tool times out, try PDFtk on Windows. If one PDF is corrupted, the merge may fail — try opening that PDF in Preview or Adobe Reader first to confirm it opens correctly. If it does not, the file itself may be damaged and need to be re-created or re-downloaded from its source.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.