How to Combine Multiple PDFs Into a Single File

The fastest way depends on what you already have installed

You can combine PDFs using free software that's already on your computer, or through a web browser without installing anything. On Windows, the built-in Print to PDF feature works if you open each file and print it to a new document — but this is slow for many files. On Mac, Preview (the default image viewer) lets you drag PDFs into a sidebar and export them as one. For any operating system, free desktop programs like PDFtk or Ghostscript do the job in seconds once you learn the command. If you prefer not to install software, web tools like ILovePDF or Smallpdf let you upload files and download the combined result.

The trade-off is between speed and privacy. Desktop software keeps your files on your computer. Web tools are faster to start using but send your PDFs to someone else's server — which matters if the documents contain sensitive information like tax returns or medical records.

Key Takeaways

Mac users can open Preview, drag multiple PDFs into the sidebar, then export as a single file in under a minute.
Windows users without extra software can print each PDF to a new document, but this is slower than using a free desktop tool.
Free desktop programs like PDFtk (Windows, Mac, Linux) combine files from the command line and keep your documents on your own computer.
Web-based tools like ILovePDF require no installation but upload your files to their servers, which is a privacy trade-off for sensitive documents.
The order of files in the combined PDF depends on the order you select them — most tools let you drag to rearrange before combining.

Using Preview on Mac

Open the first PDF in Preview (double-click it, or right-click and select "Open With" > "Preview"). Go to View menu and select "Thumbnails" to show a sidebar with page thumbnails. Drag the other PDF files directly into this sidebar — they'll appear as new pages at the end. You can drag individual pages or entire files to reorder them. When you're done, go to File > Export As, choose PDF as the format, name your file, and click Save.

This method works for any number of files and takes a few minutes for 5 to 10 PDFs. Preview doesn't compress the files, so the combined PDF will be roughly the sum of the original file sizes.

Using Print to PDF on Windows

Open the first PDF in any reader (Windows Reader, Adobe Reader, or your browser). Press Ctrl+P to open Print. Under "Printer," select "Print to File" or "Microsoft Print to PDF." Click Print and save the file with a new name. Open the second PDF, repeat the process, but this time in the Print dialog, look for an option to "Append to existing file" or similar — not all PDF readers offer this. If your reader doesn't have append, you'll need to use a different method.

This approach is slower than desktop software because you're opening and printing each file individually. It's useful only if you have just two or three PDFs and no other tools installed.

Using PDFtk on Windows, Mac, or Linux

PDFtk is a free command-line tool that combines PDFs in seconds. Download it from pdftk.com and install it. Open your terminal (Command Prompt on Windows, Terminal on Mac or Linux). Navigate to the folder where your PDFs are stored using the cd command. Then type: pdftk file1.pdf file2.pdf file3.pdf cat output combined.pdf — replacing the filenames with your actual PDF names, in the order you want them combined.

The files combine in the order you list them. If you have many PDFs, you can also use a wildcard: pdftk *.pdf cat output combined.pdf will combine all PDFs in that folder, though the order depends on how your operating system sorts filenames. This method is fastest for large batches and keeps everything on your computer.

Using a web tool like ILovePDF or Smallpdf

Go to ilovepdf.com or smallpdf.com in your browser. Look for the "Merge PDF" or "Combine PDF" option. Click the button to upload files, select all the PDFs you want to combine, and they'll appear in a list. Drag them to reorder if needed. Click the Merge or Combine button, wait for processing (usually 10 to 30 seconds), and download the result.

These tools require no installation and work on any device with a browser. The downside is that your files are uploaded to their servers during processing. Most of these services delete files after a few hours, but if your PDFs contain tax information, medical records, or other sensitive data, this is a privacy risk. Check the site's privacy policy before uploading. For non-sensitive documents like scanned receipts or public articles, web tools are the fastest option.

Choosing the right order before combining

Most tools let you arrange files before combining. In Preview, drag pages in the sidebar. In PDFtk, list files in the order you want them. On web tools, drag files in the upload list. If you're combining many files and order matters, number them before you start: rename them to 01-invoice.pdf, 02-receipt.pdf, 03-statement.pdf. This way, even if you use a wildcard command or upload all at once, they'll combine in the right sequence.

If you combine files in the wrong order, you'll need to start over — most tools don't let you reorder after combining. The exception is if you use a tool that exports to a format you can edit later, like opening the combined PDF in Preview again and removing unwanted pages.

Reducing file size after combining

Combined PDFs are often larger than you need, especially if the original files contain high-resolution images or were scanned at high quality. If the combined file is too large to email or store, you can compress it. On Mac, open the combined PDF in Preview, go to File > Export, and under "Quartz Filter," select "Reduce File Size." On Windows or any system, use a free online tool like Smallpdf's Compress PDF feature, or use Ghostscript from the command line with: ghostscript -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -o output.pdf input.pdf.

Compression trades quality for size. The "ebook" setting reduces file size significantly but may blur text or images. Test on a copy first to see if the result is acceptable for your use.

Frequently Asked Questions

Can I combine PDFs that have different page sizes?

Yes. All methods handle mixed page sizes — a letter-size page and a tabloid page will combine without error. The combined PDF will preserve each page's original size, so when you open it, pages may appear at different zoom levels depending on your reader's settings.

What if one of my PDFs is password-protected?

You'll need to remove the password first. If it's a password you know, open the PDF in Adobe Reader, go to File > Properties > Security, and remove the password. If you don't know the password, you cannot combine it legally. Web tools and desktop software cannot bypass password protection.

Does combining PDFs change the original files?

No. Combining creates a new file. Your original PDFs remain unchanged on your computer. Make sure you save the combined file with a different name so you don't accidentally overwrite an original.

How large can the combined file be?

Desktop tools like PDFtk and Preview can handle files of several hundred megabytes without issue. Web tools usually have upload limits between 100 MB and 2 GB per file, depending on the service. Check the tool's limits before uploading very large files.

Can I combine PDFs on my phone or tablet?

Yes, but options are limited. On iPad, the built-in Files app and some PDF readers like GoodNotes let you combine files. On Android, apps like PDF Merger or Adobe Acrobat Reader offer combining features. Web tools work on mobile browsers too, though uploading multiple files at once can be slower on a phone.

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.