How to merge PDF files without uploading them

Published October 21, 2026

Merging PDFs is one of the most common document tasks: a job application with a cover letter, CV and certificates, an expense claim with a stack of receipts, or a contract with its appendices. It’s also a task where the files are often personal.

Most online merge tools upload your files to a server, combine them there, and send the result back. You don’t need to do that. A merge is simple enough to run entirely on your own computer or phone. This guide covers three private ways to do it, then some tips for getting the result right.

Option 1: merge in your browser with LeafLock

Merge PDF runs in your browser. The files are read and combined on your device, and nothing is uploaded. It works in any modern browser on a computer, tablet or phone, with no software to install.

1. Open Merge PDF.
2. Choose the PDF files you want to combine. You can select several at once.
3. Put them in order with the arrow buttons. The file at the top becomes the start of the new document.
4. Select Merge PDFs and download the result.

If you’d like to confirm that nothing is sent anywhere, follow our guide on how to check if a PDF site uploads your files. The offline test is the quickest: load the page, disconnect from the internet, and merge.

Option 2: macOS Preview

Every Mac includes Preview, which can combine PDFs without any extra software.

1. Open the first PDF in Preview.
2. Choose View > Thumbnails to show the page sidebar.
3. Drag another PDF file from Finder onto the sidebar. Drop it where you want its pages to go: between two thumbnails, or after the last one.
4. Repeat for any other files. You can drag thumbnails up and down to reorder pages.
5. Choose File > Export as PDF to save the combined document as a new file.

Exporting to a new file is safer than saving over the original. Preview edits the open document directly, so if you just close it, you may change your first file without meaning to.

You can also select several PDFs in Finder, right-click, and choose Quick Actions > Create PDF. This combines them in the order they’re sorted in Finder, so rename them first (for example 1-cover.pdf, 2-cv.pdf) if the order matters.

Option 3: Windows

Windows doesn’t include a built-in way to merge PDFs. Microsoft Edge can open and annotate PDFs, and “Microsoft Print to PDF” can create them, but neither combines several files into one.

Your choices on Windows are a browser-based tool that works locally, such as Merge PDF, or installing desktop PDF software. If you install software, check that it comes from the publisher’s own website.

Get the order right

The order is the part people most often get wrong, and it’s easy to miss until someone else points it out.

• Name files with numbers first. 01-cover-letter.pdf, 02-cv.pdf, 03-references.pdf sort correctly everywhere. Use two digits if you have ten or more files, so 10 doesn’t land before 2.
• Decide the order before you merge. Write a short list if there are many files. Reordering pages afterward is possible, but slower.
• Fix individual pages after merging. If one page is out of place, or a scan is upside down, use Organize PDF to drag pages into position, or Rotate PDF to turn them.
• Remove what you don’t need. Blank pages from double-sided scanning, or a cover sheet nobody asked for, can go with Remove pages.
• Check the result. Open the merged file and scroll through every page before you send it.

Keep the file size under control

A merged PDF is usually about as big as all the input files added together. Merging doesn’t compress anything, so five 4 MB scans make a file of around 20 MB. That can be too large for email or an upload form.

Some tips:

• Compress the scans, not the text documents. Files exported from Word or another editor are usually small already. Scans and photos are what make a PDF big.
• Compress after merging. Run the merged file through Compress PDF once, rather than compressing each input separately. You can see the size before and after.
• Scan at a sensible resolution. 200 to 300 DPI is plenty for most paperwork. Scanning at 600 DPI makes files much larger without making them easier to read.
• Check the limit before you send. If a form says “maximum 10 MB”, aim a little below that.

Our guide to compressing a PDF for email explains the compression levels in more detail.

Common problems

A file is password-protected

If a PDF needs a password to open, it must be unlocked before it can be merged. If you know the password, use Unlock PDF first, then merge the unlocked copy. You can’t remove a password you don’t know, and you shouldn’t try with someone else’s document.

Bookmarks or form fields behave differently

Merging combines pages. Extras attached to the whole document, such as the bookmark sidebar, may not carry over in the same way. If you’re combining fillable forms, fill them in first, then use Flatten PDF so the answers become part of the page before merging.

Some of your files are images

Photos of receipts or documents as JPG or PNG files need to become PDFs first. Use JPG to PDF to convert them, then merge the result with your other files.

Summary

1. For a private merge on any device, use Merge PDF. It runs in your browser and doesn’t upload your files.
2. On a Mac, Preview can also do it: add files in the thumbnail sidebar, then export.
3. Windows has no built-in merge, so use a local browser tool or installed software.
4. Number your files, check the order, and compress the result if it’s too big to send.