How to merge PDF files for free, without uploading them
By the OpenToolbox team · Updated · 6 min read
In short
To merge PDF files, open a PDF merger, add the files, drag them into the order you want and download the combined document. With OpenToolbox's Merge PDF this happens inside your browser: nothing is uploaded, there is no sign-up, and you can take only some pages from each file by typing ranges such as 1-3, 5.
Key points
- Merging copies whole pages: text stays selectable and images keep their original quality.
- You can merge only some pages of each file with ranges like
1-3, 5,8-orlast. - Password-protected PDFs must be unlocked first; bookmarks and fillable form fields are not carried over.
- A browser-based merger that runs locally is the safest choice for contracts, invoices and ID scans.
Step by step
Open the tool
Go to Merge PDF. It works in any modern browser on Windows, macOS, Linux, Android and iOS.
Add your PDFs
Drop the files on the page or click to choose them. You need at least two; you can add more later with Add more PDFs.
Put them in order
Drag the file cards, or use the up and down arrows, until they are in the order you want in the final document.
Pick pages (optional)
Under each file name, type the pages to keep, for example
1-3, 5. Leave the field empty to keep every page.Merge and download
Type a name for the new file and click Merge PDFs. The combined PDF downloads as soon as it is ready.
What actually happens when you merge PDFs
A PDF is a set of independent pages. Merging creates a new, empty document and copies the pages of each file into it, one file after the other. Nothing is converted or re-rendered: fonts, vector drawings and pictures are copied as they are, so the merged file looks exactly like the originals and its text can still be selected and searched.
Because the pages are copied rather than re-compressed, the merged PDF weighs about as much as the files you put in. In our test, three scanned PDFs totalling 33.4 MB became one 30-page file of 33.4 MB, about 18 KB smaller than their sum, in 1.9 seconds. If you need a smaller file, run it through Compress PDF afterwards.
Merging only some pages: the range syntax
Every file in the list has a page field. It accepts single pages and ranges separated by commas, semicolons or spaces, and the pages are added in the order you write them:
| You type | Pages taken | Useful for |
|---|---|---|
1-3, 5 | 1, 2, 3, 5 | Skipping one page in the middle |
8- | 8 to the last page | Dropping a cover or a table of contents |
-3 | 1, 2, 3 | Keeping only the first pages |
last | The last page only | Taking a signature page |
5-3 | 5, 4, 3 | Reversing pages scanned back to front |
1, 1 | Page 1 twice | Repeating a page, such as a separator |
If a range points past the end of the file, the field turns red and tells you how many pages the PDF has, so you can fix it before merging. The Pages counter next to the button shows how many pages the merged file will have.
Why it matters that the files are not uploaded
Many online PDF services send your files to their servers, process them there and keep them for a while. That is a problem for exactly the documents people merge most often: contracts, payslips, bank statements, medical reports and scans of ID cards.
OpenToolbox's merger is a web page that does the work with JavaScript on your own device. You can check it yourself in your browser’s developer tools: the Network tab shows no request carrying your files. They never leave your computer or phone, and closing the tab clears them from memory.
Other ways to merge PDFs
You do not always need a website. Here is what each system offers out of the box:
| Method | Cost | Page selection | Notes |
|---|---|---|---|
| Merge PDF in the browser | Free | Yes, with ranges | Any device, files stay local |
| Preview on macOS | Free, built in | Yes, by dragging thumbnails | Open the first PDF, show the sidebar thumbnails, drag the other files into it |
| Windows | — | — | No built-in way to merge PDFs; use a browser tool or a PDF editor |
| Adobe Acrobat | Paid (Standard / Pro) | Yes | Combine Files; also keeps bookmarks |
qpdf command line | Free, open source | Yes | qpdf --empty --pages a.pdf b.pdf -- out.pdf |
pdfunite (Poppler) | Free, open source | No | pdfunite a.pdf b.pdf out.pdf |
The command-line tools are the best choice for scripts and very large batches. For a few files, a local browser tool is the quickest option that works the same on every device.
Common problems and how to fix them
- “Encrypted” or “Password-protected”. The PDF has a password or editing restrictions, and a browser cannot change it without removing them. If you know the password, remove it with Unlock PDF, then add the unlocked file.
- A file is refused as damaged. Open it in a PDF reader and save or print it as a new PDF, then try again. Files that were only partly downloaded are the usual cause.
- The pages are in the wrong order inside one file. Merge first, then reorder or delete pages of the result with Rotate PDF, which also lets you rotate sideways scans.
- The merged file is too big for email. Compress it with Compress PDF: the Ebook level (150 DPI) usually shrinks scanned documents a lot while keeping them readable.
- Bookmarks or form fields disappeared. The merger copies page content, links and annotations, but not the outline (bookmarks) or interactive form fields. Fill in and flatten forms before merging if you need their values.
When you need the opposite
If you have one long PDF and want several smaller ones, use Split PDF. To turn photos or scans into a PDF before merging, use Image to PDF.
How we tested
We ran every test on 24 October 2026 with the tool exactly as published, in Chrome 152 on a desktop PC (AMD Ryzen 7 5700X, NVIDIA GeForce RTX 5060, 32 GB of RAM). Sizes are the ones the tool shows (1 MB = 1,048,576 bytes); times include reading the files.
We merged three real scans of different kinds: a 5-page letter scanned at 300 DPI (16.3 MB), a 21-page pamphlet (5.0 MB) and a 4-page book scan from the Internet Archive that uses JPEG 2000 and JBIG2 images (12.1 MB). The tool reported 30 pages and 33.4 MB, with the files in the order we set.
We also checked the page-range field with 1-3, 5 on the pamphlet: only those four pages were taken, in that order, and the page counter dropped accordingly.
Test files
- Letter of the Italian Navy, 5 pages scanned at 300 DPI (Letteraspia 1–3, Letterconsole, Lettera ambasc) (public domain · Wikimedia Commons)
- A Letter to Working Mothers, ed. 6 (21-page scanned pamphlet) (public domain · Wikimedia Commons)
- A Letter to A Gentleman in the Country, 1684 (4-page Internet Archive scan) (public domain · Wikimedia Commons)
Frequently asked questions
Is it safe to merge PDFs online?
It depends on where the work is done. Tools that upload your files process them on someone else's server. OpenToolbox's Merge PDF runs entirely in your browser, so your documents never leave your device.
How many PDFs can I merge at once?
There is no fixed limit. The practical limit is your device's memory: dozens of ordinary documents are fine on a laptop or a recent phone, while hundreds of large scans may need a desktop computer.
Does merging reduce the quality?
No. Pages are copied without re-compressing anything, so text, vector graphics and images keep their original quality.
Can I merge PDFs on my phone?
Yes. The tool works in the browser on Android and iOS: choose the files from your phone's storage or cloud folders, order them and download the merged PDF.
How do I merge only certain pages?
Type the pages in the field under each file name, for example 1-3, 5 or 10- for page 10 to the end. Only those pages of that file go into the merged document, in the order you typed them.