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How to merge PDF files into one
This merge PDF tool combines two or more PDF documents into a single file, right in your browser. It takes three steps:
- Choose your PDF files, or drop them on the box. You can add several at once and add more later.
- Check the order. Each file shows its page count, and the arrow buttons move it up or down. The file at the top comes first in the merged document.
- Press Merge PDF, then Download merged PDF. The new file is named after your first file with -merged at the end, so your originals stay untouched.
Want to see how it works first? Use the sample button to load two small example PDFs and merge them.
What happens to your files
Most online PDF mergers upload your documents to a server, process them there and send back the result. This page works differently: the PDF engine (the open source pdf-lib library) is downloaded once and runs on your own device. Your files are read from your disk into memory, the pages are copied into a new document, and the result is offered as a download. Nothing is uploaded, which matters when you are combining contracts, bank statements, medical letters or scans of your passport.
Pages are copied, not re-printed. That means text stays selectable and searchable, vector drawings stay sharp and photos are not compressed again. The merged file is usually close to the total size of the files you added.
Common reasons to combine PDFs
- Job applications: many portals accept only one file, so the CV, cover letter and certificates have to go into a single PDF.
- Invoices and receipts: one document per month or per project is easier to send to an accountant.
- Scanned documents: phone scanning apps often save each page separately. Merging puts them back together.
- Reports: add a cover page, appendix or signed form to a document created elsewhere.
Files that cannot be merged
| Message | Cause | What to do |
|---|---|---|
| Password protected | The PDF is encrypted with an open or permissions password. | Open it with the password and save or print it as a new PDF, then add that copy. |
| Damaged or not a valid PDF | The download was cut off, or the file is another format renamed to .pdf. | Download it again, or open it in a PDF reader and print it to a new PDF. |
| Skipped, not a PDF | You picked a Word file or an image. | Export Word documents as PDF first. For photos, use the JPG to PDF tool. |
Files with a problem are marked in red in the list. Remove them and the rest can be merged normally.
Tips for a clean result
- Rename files with a number at the start (01-cv.pdf, 02-letter.pdf) before adding them. They will then appear roughly in the right order straight away.
- Pages keep their own size. If you mix A4 and Letter documents, the merged file contains both sizes, which is normal and prints fine.
- If the merged file is too big for an upload form, compress the scans before merging, since images make up most of the size.
- On phones, close other apps when merging very large documents. Everything happens in memory, so a few hundred pages at a time is a safe amount.
Limits
The tool merges whole documents. It does not keep bookmarks, the table of contents or links that point between files, and filled-in form fields or digital signatures may lose their special behaviour after merging, because a signature is tied to the exact original file. If a signature must stay valid, send the signed PDF as a separate file. An internet connection is needed only the first time, to load the PDF engine.
Frequently asked questions
How do I combine PDF files into one?
Add your PDF files, use the up and down arrows to put them in order, then press Merge PDF and download the new file. The pages appear in the same order as the list.
Are my PDF files uploaded to a server?
No. The files are read and merged inside your browser. Nothing is sent anywhere, so it is safe for contracts, payslips and ID scans.
Why can't a PDF be added to the merge?
The file is either password protected or damaged. Remove the password in the app that created it (or by printing it to a new PDF), then add it again.
Is there a limit on the number of files or pages?
There is no fixed limit. Very large files use more memory, so on an older phone it is best to merge a few hundred pages at a time.
Does merging reduce the quality of my PDF?
No. Pages are copied as they are, so text stays sharp and searchable and images are not recompressed. Bookmarks and form fields may not carry over.