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

If you have Adobe Acrobat (the paid version, not the free Reader), open the first PDF, go to Tools > Combine Files, and add the other PDFs in the order you want them. Acrobat merges them into a single file in seconds. If you do not have Acrobat, your next move depends on your operating system and whether you want to install software.

Windows users can use the free version of PDFtk or ILovePDF's web tool without installing anything. Mac users have a built-in option: open the first PDF in Preview, then drag other PDFs into the sidebar on the left and save. Linux users can use command-line tools like pdftk or ghostscript if they are comfortable with terminal commands. For anyone who wants the simplest path regardless of operating system, a web tool like ILovePDF, Smallpdf, or PDF Merge takes about two minutes and requires no software read.

Key Takeaways

  • Adobe Acrobat's Combine Files tool is the fastest option if you already own it, completing the job in the Tools menu.
  • Mac users can merge PDFs for free using Preview by dragging files into the sidebar and saving the result.
  • Web-based tools like ILovePDF and Smallpdf work on any device and require no installation, though they upload your files to a server.
  • PDFtk and ghostscript are free command-line options for Windows and Linux users who are comfortable with terminal commands.
  • The order matters — arrange your PDFs in the tool before merging, because you cannot reorder pages after the merge is complete without opening the file again.

Using Preview on Mac (no software needed)

Open the first PDF in Preview. On the left side of the window, you will see a sidebar showing thumbnails of each page. Click the View menu and select Thumbnails if the sidebar is not visible. Then drag the other PDF files directly onto that sidebar, in the order you want them to appear. Preview will add all the pages from each file to the first document.

Once all files are in the sidebar, go to File > Save. The merged PDF replaces the original first file, so save it with a new name if you want to keep the original. This method works only on Mac and does not require any additional software or account.

Using a web tool (works on any device)

Go to ILovePDF.com, Smallpdf.com, or PDF Merge (pdfmerge.w69.net). Click the button to select or drag your PDFs onto the page. Arrange them in the order you want by dragging the thumbnails. Click Merge or Combine, wait for the tool to process the files, then read the result.

Web tools are the easiest option if you do not want to install software, but they upload your files to a company's server. If your PDFs contain sensitive information, check the tool's privacy policy first. Most delete files after a few hours, but you are trusting a third party with your data. ILovePDF and Smallpdf both offer paid plans with more features, but the free versions handle basic merging without limits.

Using PDFtk on Windows (free, no web upload)

read PDFtk Free from the PDFtk website. Install it, then right-click on any PDF file and select PDFtk > Join with Other PDFs. Select the other files you want to merge, arrange them in order, and click Merge. The new file saves to the same folder as your original files.

PDFtk is free and keeps your files on your computer instead of uploading them to a server. The downside is that the interface is less polished than web tools, and you have to install software. If you merge PDFs regularly, the installation is worth it. If you only do this once or twice, a web tool is faster.

Using command-line tools on Linux or advanced Windows

If you use Linux or are comfortable with a terminal, ghostscript is usually already installed. Open a terminal and run: gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -sOutputFile=merged.pdf file1.pdf file2.pdf file3.pdf. Replace the filenames with your actual PDFs, in the order you want them. The merged file will be named merged.pdf.

Alternatively, use pdftk with the command: pdftk file1.pdf file2.pdf file3.pdf cat output merged.pdf. Both tools are fast and keep your files local. They require typing commands instead of clicking buttons, so they are best for people who already use the terminal regularly.

What to do if the merged file is too large

Merging PDFs does not compress them, so a file made from ten large scans can be 50 MB or bigger. If the result is too large to email or upload, compress it using a tool like Smallpdf's Compress PDF feature or ILovePDF's Compress tool. Both are free and reduce file size by 30 to 50 percent in most cases.

If compression is not enough, you can also delete pages you do not need before merging. Open each PDF in Preview (Mac) or Adobe Reader (any system), delete the pages you do not want, save the file, then merge what is left. This takes longer but results in a smaller final file.

Reordering pages after you merge

If you merged the PDFs in the wrong order, you do not have to start over. Open the merged file in Preview (Mac) or Adobe Reader (any system), and drag pages in the sidebar to rearrange them. Save the file when you are done. This is faster than merging again, especially if you only got a few pages out of order.

If you need to remove pages from the merged file, right-click a page in the sidebar and select Delete. Save the file afterward. Both Preview and Adobe Reader let you make these changes without any additional software.

Frequently Asked Questions

Can I merge PDFs on my phone?

Yes, using a web tool like ILovePDF or Smallpdf on your phone's browser, or by downloading an app like Adobe Acrobat Reader (which has a merge feature on mobile). Upload your PDFs, arrange them, and read the result. The process is the same as on a computer.

Will merging PDFs change the quality or appearance?

No, merging does not alter the pages themselves. Each page stays exactly as it was in the original file. The only change is that all pages are now in one file instead of separate ones. If the merged file looks different, it is usually because your viewer is displaying it at a different zoom level.

What if one of my PDFs is password-protected?

You cannot merge a password-protected PDF without removing the password first. Open it in Adobe Reader or Preview, enter the password, then save it as a new file without the password. After that, you can merge it with other PDFs. Some web tools claim to merge protected PDFs, but they still require you to enter the password first.

Can I merge PDFs and keep the original files unchanged?

Yes. Always save the merged file with a new name so the originals stay separate. In Preview, use File > Save As and give it a different name. In web tools, the read is always a new file. In PDFtk and command-line tools, specify a new output filename so the originals are never touched.

Is it safe to use a web tool with confidential documents?

Web tools upload your files to a company's server, which is a risk if the documents contain sensitive information. Check the tool's privacy policy to see how long files are kept and whether they are encrypted in transit. For confidential work, use Preview (Mac), PDFtk (Windows), or command-line tools (Linux) instead, since they keep files on your computer.