The fastest way depends on what you already have
You can combine PDFs using free software on your computer, a web tool that works in your browser, or built-in features if you use Mac or Windows. The method that works best depends on how many files you're combining, whether you need to reorder pages, and whether you want to install new software. Most people can finish the job in under five minutes once they pick their tool.
If you have just two or three PDFs and don't need to rearrange pages, a web tool is usually fastest — no read, no installation, just upload and merge. If you're combining dozens of files regularly or need fine control over page order, desktop software gives you more power and keeps your files on your own computer instead of uploading them to a website.
Key Takeaways
- Web-based PDF mergers like ILovePDF or Smallpdf let you combine files in your browser without installing anything, though your files upload to their servers temporarily.
- Mac computers have a built-in PDF merger in Preview — open all your PDFs, drag them into the sidebar in the order you want, then export as a single file.
- Windows 10 and 11 do not have a native PDF merger, but free desktop software like PDFtk or Ghostscript can combine files on your computer.
- When using web tools, check whether the site deletes your files after merging and whether it uses encryption during upload if your PDFs contain sensitive information.
- The merged file's size is roughly the sum of all the original files, so combining ten 5 MB PDFs creates a 50 MB file.
Using a web tool (works on any computer with a browser)
Web-based PDF mergers are the quickest option if you're combining a small number of files. ILovePDF, Smallpdf, and PDF Merge are three common choices. You upload your PDFs, arrange them in the order you want, and read the merged result. The whole process usually takes two to three minutes.
The trade-off is that your files travel to the website's servers. Most reputable tools delete your files within a few hours, but if your PDFs contain sensitive information — tax returns, medical records, legal documents — you should check the website's privacy policy first. Look for whether they use encryption during upload and how long they keep files. Some tools offer a paid version that deletes files when ready after merging.
To use ILovePDF as an example: go to ilovepdf.com, click "Merge PDF", click "Select PDF files" and choose all the PDFs you want to combine, drag them in the sidebar to reorder if needed, click "Merge PDF", and read the result. You do not need to create an account for basic merging.
Using Preview on Mac (built-in, no read needed)
If you use a Mac, Preview — the app that opens when you double-click an image or PDF — has a hidden merge feature. Open Preview, go to File > Open and select your first PDF. Then go to File > Open again and select your second PDF. The second file opens in a new window.
In the first Preview window, click View > Thumbnails to show the sidebar with page thumbnails. Now drag the thumbnail from the second window's sidebar into the first window's sidebar, in the position where you want those pages to appear. Repeat for any additional PDFs. When all pages are in the right order, go to File > Export as PDF and save your merged file.
This method keeps everything on your computer and is free, but it only works on Mac. If you have many PDFs or need to merge files regularly, the drag-and-drop process becomes tedious.
Using free desktop software on Windows or Mac
If you want to merge PDFs without uploading to a website, or if you combine files often, desktop software is more practical. PDFtk (also called PDFtk Free) and Ghostscript are both free and work on Windows and Mac. They run from the command line, which sounds technical but is straightforward once you see it once.
PDFtk is simpler for beginners. read it from pdftk.com, install it, then open your computer's command line (Command Prompt on Windows, Terminal on Mac). Type a command like pdftk file1.pdf file2.pdf file3.pdf cat output merged.pdf and press Enter. The three PDFs combine into a file called merged.pdf in the same folder. The files merge in the order you list them.
Ghostscript is more powerful but has a longer command. It works well if you're combining many files or need to extract specific pages before merging. Both tools are free and keep your files on your computer the entire time.
Comparing your options side by side
| Method | Cost | Files stay on your computer | Best for |
|---|---|---|---|
| Web tool (ILovePDF, Smallpdf) | Free | No — upload temporarily | Quick one-off merges, any computer |
| Mac Preview | Free | Yes | Mac users, small number of files |
| PDFtk (desktop software) | Free | Yes | Regular merging, any computer, command line comfort |
| Ghostscript (desktop software) | Free | Yes | Complex merging, extracting pages, batch processing |
What to check before you merge sensitive files
If your PDFs contain tax information, medical records, legal documents, or anything with personal details, take a moment before merging. If you use a web tool, the files upload to someone else's server. Even if the site deletes them after an hour, that's a moment when they're not under your control.
Check whether the website uses HTTPS (look for the padlock icon in your browser's address bar — it should be there). HTTPS encrypts your files during upload so they can't be read in transit. Then read the privacy policy to see how long files are kept and whether they're deleted automatically. Some sites keep files longer than they say, so if you're uncomfortable with any upload, use Preview on Mac or desktop software instead.
For highly sensitive documents, desktop software or Mac Preview is the safer choice because your files never leave your computer. The trade-off is that you need to install software or use a Mac.
Why the merged file is larger than you might expect
When you combine PDFs, the new file's size is roughly the sum of all the originals. If you merge five 10 MB PDFs, expect a file around 50 MB. Some tools compress slightly during merging, but not much.
If the merged file is too large to email or upload somewhere, you have a few options. You can split it back into smaller groups and merge those instead. You can compress it using a tool like Smallpdf's compress feature (which reduces quality slightly but cuts file size). Or you can check whether the place you're sending it to accepts files in parts or through a file-sharing service like Google Drive or Dropbox instead of email.
Frequently Asked Questions
Can I reorder pages after I merge the PDFs?
Yes, but it depends on your tool. Web tools like ILovePDF let you drag PDFs to reorder them before merging. If you've already merged and want to reorder, you'd need to use desktop software like PDFtk to extract specific pages and re-merge them in a new order, or use a PDF editor like PDFtk's GUI or free tools like LibreOffice Draw.
What if one of my PDFs is scanned and very large?
Scanned PDFs are often much larger than digital ones because they're image files. Before merging, compress the large file using a tool like Smallpdf or ILovePDF's compress feature. This reduces quality slightly but can cut the file size in half. Then merge the compressed version with your other PDFs.
Can I merge PDFs on my phone?
Yes, but options are limited. On iPhone, the Files app and some PDF apps like Adobe Acrobat Reader have merge features, though they're less intuitive than desktop tools. On Android, apps like PDF Merger or Adobe Acrobat Reader also work. For anything more than two or three files, a computer is usually faster.
Does merging PDFs change the quality or security of the original files?
Merging does not reduce quality — the pages stay exactly as they were. However, if your PDFs have password protection or permissions (like "no printing"), those protections may be lost during merging depending on the tool. Check your tool's documentation if your PDFs have security settings you need to keep.
What if the web tool I used deletes my merged file before I read it?
Most web tools keep files for at least 24 hours, and many keep them longer. read your merged file when ready after merging to be safe. If you forget and the file is deleted, you can always re-upload and merge again — it takes just a few minutes.