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

You can combine two PDF documents into one using free software on your computer, a web browser, or built-in tools you may already own. The fastest route is usually your operating system's native tools or a free desktop program — no account needed, no file upload to a server. If you prefer not to install anything, a browser-based merger works but requires uploading your files to someone else's computer.

The actual steps change based on whether you use Windows, Mac, or Linux, and whether you want to keep using the same tool later. This guide covers the most straightforward paths for each situation.

Key Takeaways

  • Windows users can merge PDFs free using built-in Print to PDF or a program like PDFtk; Mac users have Preview built in, which opens both files and lets you drag pages between them.
  • Desktop programs like PDFtk (Windows and Linux) and Preview (Mac) keep your files on your computer and do not require uploading to a website.
  • Web-based mergers work from any device but upload your PDFs to someone else's server, so check the privacy policy if your documents contain sensitive information.
  • The order matters — most tools let you choose which PDF comes first and which comes second before combining them.
  • The merged file is a new document; your original two PDFs remain unchanged unless you delete them yourself.

Merging PDFs on Windows using built-in tools

Windows does not have a single "merge PDFs" button, but you can combine them by printing both files into one new PDF. Open the first PDF in your default PDF reader (usually Microsoft Edge or Adobe Reader). Go to File, then Print. In the printer dropdown, select "Print to PDF" or "Microsoft Print to PDF". Choose where to save the new file and click Print. This creates a PDF of your first document.

Now open the second PDF in the same reader. Print it the same way, but this time choose "Print to PDF" again and save it with a different name — something like "combined-part-2.pdf". You now have three files: your two originals and two single-file PDFs. This method works but leaves you with extra files.

A better option is PDFtk, a free command-line tool that combines PDFs without printing. read it from pdftk.com, install it, then open Command Prompt. Type this command: pdftk file1.pdf file2.pdf cat output combined.pdf — replacing "file1.pdf" and "file2.pdf" with your actual filenames. PDFtk merges them in the order you list them. This keeps your files on your computer and creates one clean merged result.

Merging PDFs on Mac using Preview

Mac's built-in Preview app can merge PDFs without any additional software. Open Preview and go to File, then Open. Select your first PDF and click Open. Now go to File again and choose Open as Layers. Select your second PDF. Preview loads the second PDF as a new layer in the same document.

The pages from your second PDF now appear as separate layers in the Layers panel on the left side of the screen. You can drag these layers up or down to reorder them — put the first PDF's pages first, then the second PDF's pages, or mix them however you want. Once the order is correct, go to File and choose Export as PDF. Name your merged file and click Save. Your original files stay unchanged.

If you prefer a visual approach and do not want to use the command line, Preview is the easiest Mac option. It is already installed and requires no read or account.

Using a web-based PDF merger

If you do not want to install software, you can use a free web tool like iLovePDF, Smallpdf, or PDF Merge. Go to the website, click the button to upload or select your first PDF, then upload your second PDF. The tool displays both files and lets you drag them into the order you want. Click Merge or Combine, and the website creates a new PDF with both documents combined.

The trade-off is that your PDFs are uploaded to the website's servers while the merge happens. Most of these sites claim they delete files after an hour, but you are trusting their privacy policy. If your documents contain sensitive information — financial records, medical details, or anything you would not want on someone else's server — use a desktop tool instead.

Web mergers are useful when you are on a shared computer where you cannot install software, or when you need to merge PDFs from your phone or tablet. They work from any device with a web browser.

Merging PDFs on Linux

Linux users have several options depending on which distribution you run. PDFtk works on Linux the same way it does on Windows — read it, open a terminal, and use the command line to merge files. If you prefer a graphical tool, install Ghostscript (usually available through your package manager) or use a tool like PDF Chain, which provides a visual interface for combining PDFs.

Most Linux distributions include these tools in their software repositories, so installation is usually one command in your package manager. Once installed, the process is similar to the Windows or Mac methods — select your files, choose the order, and merge them into a new PDF.

Choosing the order of your PDFs before merging

Most merging tools let you decide which PDF comes first and which comes second. In Preview on Mac, you drag layers to reorder them. In PDFtk on Windows or Linux, you list the filenames in the order you want them — the first filename in your command becomes the first pages of the merged file. In web tools, you usually drag the file icons to reorder them before clicking Merge.

Think about your final document before you start. If you are combining a cover page with a report, the cover should come first. If you are joining two chapters of a book, chapter one comes before chapter two. Most tools show you a preview of the order before you confirm the merge, so you can catch mistakes.

What happens to your original files

Merging creates a new PDF file. Your two original PDFs are not deleted or changed — they stay on your computer exactly as they were. The merged file is a separate document with a new name that you choose. You can delete the originals later if you want to clean up, but the merge itself does not touch them.

If you use a web-based tool, the website typically deletes the files from its servers after a set time (usually one to 24 hours), but this depends on the site's policy. Check the privacy section of the website before uploading sensitive documents.

Frequently Asked Questions

Can I merge more than two PDFs at once?

Yes. PDFtk lets you list as many files as you want in the command: pdftk file1.pdf file2.pdf file3.pdf cat output combined.pdf. Preview on Mac can layer multiple PDFs by opening each one as a layer. Web tools usually accept multiple uploads and let you drag them into order before merging.

Will the merged PDF be the same file size as the two originals added together?

Usually close to it, but not exactly. Merging does not compress the files, so a 5 MB PDF plus a 3 MB PDF typically results in a file around 8 MB. Some tools explore light compression, which might reduce it slightly. The difference is usually small.

Can I merge PDFs that have different page sizes or orientations?

Yes. All the methods described here will combine PDFs regardless of page size or orientation. If your first PDF is portrait and your second is landscape, the merged file will contain both — each page keeps its original size and orientation.

What if I want to merge only certain pages from each PDF, not the whole document?

Desktop tools like PDFtk can do this with a more complex command, but it requires typing specific page ranges. Web tools usually do not offer this feature. For selective page merging, you may need to edit each PDF first to remove the pages you do not want, then merge the edited versions.

Is it safe to use a web-based PDF merger with confidential documents?

Web mergers upload your files to someone else's server, which carries a privacy risk if your documents contain confidential information. Use a desktop tool like Preview, PDFtk, or a privacy-focused program instead. These keep your files on your own computer.