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

You can combine PDF files on your own computer using software you control, or you can upload them to a web service that does it for you. The trade-off is straightforward: doing it locally keeps your documents off someone else's server, but requires software installed on your device. Using a web tool is faster and works from any browser, but your files pass through their system — and you have to trust their privacy policy.

Most people can combine PDFs in under five minutes using free tools that don't require an account. The method you choose depends on what operating system you use, whether you want to keep the files on your computer, and how comfortable you are with your documents being uploaded temporarily.

Key Takeaways

  • Windows users can combine PDFs using Microsoft Edge (built-in, no upload) or free software like PDFtk or Ghostscript (requires installation).
  • Mac users have Preview, which is already on your computer and requires no upload or account.
  • Web-based tools like Smallpdf, ILovePDF, and PDF.io work from any device but send your files to their servers temporarily.
  • If privacy is your main concern, use Preview on Mac or a desktop tool on Windows — your files never leave your computer.
  • Most free tools let you combine up to 20 or 30 files at once, though some limit file size to 25 MB per document.

Combining PDFs on Mac using Preview

Preview is the fastest method if you use a Mac. It's already installed, requires no account, and your files stay on your computer. Open Preview, go to File > Open, and select all the PDFs you want to combine. They will appear as separate pages in a single Preview window. You can drag pages between documents to reorder them, then save the result as a new PDF.

If you have PDFs already open in separate Preview windows, you can also drag pages from one window into another. Right-click the thumbnail panel on the left side of Preview to see all pages, then drag them into the order you want. When you're done, go to File > Export As, choose PDF from the format dropdown, and save with a new filename so you don't overwrite the originals.

Combining PDFs on Windows without uploading

Windows doesn't have a built-in PDF tool like Preview, but Microsoft Edge (the browser that comes with Windows 10 and later) can combine PDFs without uploading them. Open Edge, go to the three-dot menu, select Print, then choose "Save as PDF" from the printer dropdown. You can then add multiple PDFs to the print queue before saving — though this method works best if you're comfortable with print dialogs.

A more straightforward option is to read free desktop software. PDFtk (available at pdftk.com) and Ghostscript (ghostscript.com) both run on Windows and let you combine files from the command line or through a graphical interface. Both are free, open-source, and keep everything on your computer. PDFtk has a simpler interface for beginners; Ghostscript is more powerful but requires more technical knowledge. Neither requires an account or internet connection after installation.

Using web-based tools when you don't mind uploading

If you prefer not to install software, web tools are faster and work on any device. Smallpdf, ILovePDF, and PDF.io all let you drag and drop multiple PDFs, reorder them, and read the combined file. You don't need an account for most of them, though creating one lets you save your work and access it later.

The trade-off is that your files are uploaded to their servers while they process. Most of these services delete files after a few hours, and many claim they don't store or share your documents — but you are trusting their privacy policy and their security. If your PDFs contain sensitive information (medical records, financial documents, legal papers), using a web tool means those files briefly exist on someone else's server. Read the privacy policy before uploading anything you wouldn't want a third party to see.

File size limits vary: Smallpdf allows up to 500 MB per file, ILovePDF allows up to 100 MB, and PDF.io allows up to 50 MB. Most let you combine 20 to 30 files in one batch. If you have very large files or many documents, desktop software is usually faster.

Reordering pages and removing unwanted pages

Most tools let you reorder pages before combining. In Preview on Mac, drag the page thumbnails on the left side into the order you want. In web tools, drag the file boxes or page previews to reorder them. Some tools also let you delete individual pages from a PDF before combining — useful if you want to skip a cover page or blank page.

If you need to remove pages from a PDF before combining, Preview on Mac has a built-in option: select the page thumbnail you want to delete and press Delete. For Windows, you may need to use a separate tool or do it in the web tool itself. Most web-based PDF tools have a delete button next to each page preview.

What to do if the combined file is too large

If your combined PDF is larger than you expected, you have a few options. Some tools let you compress the PDF after combining — this reduces file size but may lower image quality. Preview on Mac has a Quartz filter for this: go to File > Export As, click the Quartz Filter dropdown, and select "Reduce File Size." Web tools like Smallpdf and ILovePDF have compression built in.

Another option is to combine fewer files at once. If you're combining 30 PDFs and the result is too large, try combining them in smaller batches of 5 or 10, then combine those results. This takes longer but gives you more control over file size. You can also check whether any of the original PDFs are unnecessarily large — scanned documents with high resolution settings often take up much more space than needed.

Keeping track of your combined files

When you combine PDFs, give the new file a clear name that describes what it contains and when you made it. Instead of "combined.pdf", use something like "2024-tax-documents-combined.pdf" or "project-proposals-jan-to-mar.pdf". This makes it easier to find later and tells you at a glance what's inside.

Keep the original files until you're sure the combined version is correct. If you need to add or remove a page later, you'll have the originals to work from. Once you're confident the combined file is what you need, you can delete the originals if you want to save space — but there's no harm in keeping them.

Frequently Asked Questions

Can I combine PDFs that have different page sizes?

Yes. Most tools will combine them as-is, which means you might end up with some pages in letter size and others in legal size. The combined file will still open and print correctly, though the pages won't all be the same size. If you need uniform sizing, you'll need to resize the PDFs before combining them, which requires a more advanced tool.

Will combining PDFs change the security or passwords on them?

If the original PDFs are password-protected, most tools won't let you combine them without entering the password first. Once combined, the new file usually has no password protection unless you add it afterward. If you need the combined file to be password-protected, you'll have to set that up separately after combining.

What's the difference between combining and merging?

These terms mean the same thing in the context of PDFs. Both refer to taking multiple PDF files and putting them into one file. Some tools use "merge," others use "combine" — the result is identical.

Can I combine PDFs on my phone?

Yes, but it's slower than on a computer. On iPhone, use the Files app to open PDFs, then use a web tool like Smallpdf or ILovePDF from Safari. On Android, read a PDF combining app from the Google Play Store — search for "PDF merger" or "combine PDF." Desktop tools are faster if you have a computer available.

Do I need to buy software to combine PDFs?

No. Preview on Mac is free and built-in. On Windows, PDFtk and Ghostscript are free and open-source. Web tools like Smallpdf, ILovePDF, and PDF.io offer free versions that work for most people. You only need to pay if you want advanced features like batch processing hundreds of files at once or removing pages from encrypted PDFs.