PDFStack Tool

Merge PDF Files Online — Free & Private

Combine any number of PDF documents into a single, perfectly ordered file in seconds. PDFStack's merge tool runs entirely inside your browser — your files never leave your device, no account required, and there's no file-size cap imposed by a server.

Open Merge PDF →
No file uploads No account required Free to use Private & secure

Why use PDFStack to merge PDFs?

Most online PDF mergers upload your documents to a third-party server, where they sit on disk until a scheduled cleanup script (hopefully) deletes them. PDFStack is different: the entire merge operation happens in your browser using pdf-lib, a battle-tested JavaScript library. The moment you click Merge, your files are processed locally and the output is handed straight back to you — nothing ever touches our infrastructure.

How to merge PDF files

  1. 1Click Open Merge PDF above or choose Merge PDF from the tools grid.
  2. 2Drop your PDF files onto the upload zone, or click to browse and select them.
  3. 3Drag the file cards to set the exact order you want.
  4. 4Click Merge PDFs and download your combined document immediately.

All processing happens locally in your browser — no files are uploaded to any server.

Common Uses

Merging PDFs is useful for combining chapters of a report, assembling invoices into a single statement, packaging a portfolio, or joining scanned pages into one file.

Frequently Asked Questions

Is there a limit to how many PDFs I can merge?
No. Because PDFStack runs in your browser there is no server-imposed file count or size limit. The practical limit is your device's available RAM.
Will the merge preserve my PDF bookmarks and metadata?
Yes. PDFStack uses pdf-lib which retains existing page content, annotations, and metadata from each source document.
Do I need to create an account?
No account, no email, no signup of any kind is required. Open the tool and start merging.
Is my data private?
Completely. Files are processed locally in your browser and are never uploaded to any server.

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