Merge PDFs online, for free

Merging several PDFs into one document is one of the most requested operations on a PDF file: combining a resume and cover letter, gathering the supporting documents for an application, or combining several chapters of a report written separately. Technically, the operation copies, in the chosen order, every page of each source document into a new PDF file — without recompressing or re-encoding their content, which preserves the original quality (selectable text, images at their native resolution, embedded fonts).

Why this tool works without sending your files

Most online PDF merging tools work by sending your files to a server, which processes them then sends back the result — a privacy concern for documents that are sometimes sensitive (contracts, ID documents, payslips). This tool instead uses a JavaScript library, pdf-lib, able to read and assemble PDF files directly in your browser's memory. The result: merging is instant (no upload time or server wait), works even with no internet connection once the page has loaded, and above all, your files never leave your computer or phone.

What happens technically during the merge

Each PDF file you add is first loaded into memory and analysed to extract its list of pages, shown as thumbnail previews. You can then drag and drop these thumbnails to set the final order — including mixing pages from several source documents in an arbitrary order, not just document by document. Once the order is confirmed, pdf-lib copies the internal structure (the PDF object tree) of each source page into a new document, with no image recompression or text alteration: the merged file has the same quality as the originals, give or take a few bytes tied to the PDF container's own structure.

Limitations to know about

Merging preserves each page's content but doesn't automatically rebuild a unified table of contents if your source documents each had their own bookmarks. If your source PDFs have different page sizes (an A4 and a Letter, for instance), the merged file will keep that inconsistency page by page rather than standardising the dimensions — which matches what's expected in the vast majority of cases (you want the original document back as-is, not distorted).

Frequently asked questions

Are my PDF files sent to a server to be merged?
No. Merging uses a JavaScript library (pdf-lib) that builds the new document directly in your browser. You can verify this yourself: open your browser's developer tools Network tab before merging, and see that no request is sent during the operation.
How many files can I merge at once?
There's no strict limit on the tool's side: the real limit depends on the memory available in your browser, which generally handles several dozen files of a few megabytes each without trouble. For very large documents (several hundred combined megabytes), performance depends on your device.
Can I choose the order of the documents in the merged file?
Yes: after adding your files, drag and drop their thumbnails to reorder them before starting the merge. The order shown is exactly the final document's order.
Does merging keep the original PDFs' links and bookmarks?
Each page's text, images, and layout are kept identical. Internal bookmarks (a clickable table of contents) and hyperlinks internal to a document, however, aren't systematically rebuilt in the merged file, a common limitation of pdf-lib-based merging tools.
Can I merge a password-protected PDF?
No, not directly: an encrypted PDF must first be unlocked with its password (see our dedicated tool) before it can be merged, opened, or edited by any tool, including this one.
What happens if I close the tab while merging?
Nothing is kept: since no file is sent to a server, closing the tab before the operation finishes simply interrupts the processing under way, with no trace or partial file left anywhere.

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