Merge PDF
Merge PDF files online for free. Combine multiple PDFs into a single document — 100% private, files never leave your browser.
Click to choose files or drag & drop here
PDF files only · processed privately on your device
Merging PDFs is one of the most common document tasks there is — combining scanned pages into one file, assembling an application pack, or turning a set of receipts into a single expense claim. Most online tools do it by uploading your file to a server, processing it there, and asking you to trust their deletion policy.
This one does not upload anything. The merge runs entirely inside your browser using the PDF-lib library, and your files never leave your device. Because the work happens in your browser, this tool is safe for documents you would never upload to a random website — contracts, payslips, medical records, bank statements, passport scans. Nothing is transmitted, so there is no server copy to be retained, indexed or breached.
How to use the Merge PDF
Add your PDF files
Drag them onto the drop zone or click to browse. You can select several at once, and add more afterwards.
Put them in the right order
Drag the file cards to reorder. The merged document follows the order shown, top to bottom.
Click Merge
A progress bar tracks the work. Large files take a few seconds because everything is processed locally by your own device.
Download the combined PDF
The result downloads straight to your device. Nothing is stored anywhere else.
What is preserved when merging
| Element | Preserved? | Notes |
|---|---|---|
| Page content and layout | Yes | Pages are copied exactly, with no re-rendering or quality loss |
| Embedded fonts | Yes | Fonts travel with the pages they belong to |
| Images | Yes | Copied at original resolution, never recompressed |
| Page size and orientation | Yes | Mixed sizes are allowed in one document |
| Form fields | Partly | Fields are retained but duplicate field names across files can conflict |
| Digital signatures | No | Any signature is invalidated — this is by design, since the document changed |
| Bookmarks and outlines | No | The outline tree is not carried across |
Why in-browser processing matters here
PDFs are the format people use for exactly the documents they should be most careful with. A typical upload-based converter transmits your file to a server in another jurisdiction, where it sits for anywhere from an hour to indefinitely depending on the operator’s policy — and where a misconfiguration can expose it publicly.
Local processing removes the question entirely. There is no upload, no queue, no retention period and no third-party sub-processor. It is also faster for large files, because nothing has to travel over your connection twice.
Getting the page order right
- Name files so they sort naturally before adding them —
01-cover.pdf,02-report.pdf. Note that10sorts before2unless you pad with a leading zero. - Scan double-sided documents in two passes — all odd pages, then all even — and merge the two files if your scanner cannot interleave automatically.
- Check the first and last page of the output. Those are where ordering mistakes are most visible and most embarrassing.
- Merge in stages for very large jobs, combining sections first and then the sections together. It is easier to correct an error in a ten-file batch than a hundred-file one.
Keeping the file size down
A merged PDF is roughly the sum of its parts, since the pages are copied without recompression. If the result is too large for an email attachment — most providers cap at 20–25 MB — the size is almost always coming from scanned images rather than text.
Scanning at 300 DPI in colour produces very large files. For text documents, 200 DPI in greyscale is usually indistinguishable and a fraction of the size. If your pages are already images, the image compressor can shrink them before you convert back with images to PDF.
Frequently asked questions
Are my files uploaded to a server?
No. The entire merge happens inside your browser using local JavaScript. Your documents never leave your device, which is why this is safe for contracts, payslips and identity documents.
Is there a file size or count limit?
There is no artificial limit — the practical ceiling is your device’s available memory. Merging dozens of documents or files of several hundred megabytes works, but will use noticeable RAM while it runs.
Can I reorder the files before merging?
Yes. Drag the file cards into the order you want; the merged document follows that order exactly.
Does merging reduce quality?
No. Pages are copied byte for byte with no re-rendering or recompression, so text stays selectable and images keep their original resolution.
Can I merge password-protected PDFs?
Not while they are encrypted. Open the file in a PDF reader, remove the password with the owner’s permission, save an unprotected copy, then merge that.
Will my digital signature survive the merge?
No, and it should not. A signature certifies a specific document; combining it with other pages changes the document, so the signature is correctly invalidated. Re-sign the merged file if you need it certified.
Does it work offline?
Yes. The site is a progressive web app — once visited, it can be installed and used with no connection at all.
Can I merge images and PDFs together?
Convert the images first with images to PDF, then merge the resulting file with your other documents here.
100% private. Files are processed on your device and never uploaded.
Instant results. No upload queue. Processing time depends on your device.
Free forever. No signup, no watermark, no paid tier.
Works everywhere. Use a modern browser on your phone or computer.
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Merge PDF is one of all the free tools on ToolNest. No account or subscription needed — anywhere in the world.