How-to Guide · PDF

How to Merge PDF Files Online — Free on Any Device

5 min read · Updated October 2026

Combining multiple PDF documents into a single file is one of the most common document tasks — and you can do it for free, right in your browser, without installing anything. This guide shows you how to merge PDFs on Windows, Mac, Android and iOS in under two minutes.

What you need

  • A modern browser (Chrome, Firefox, Edge, Safari)
  • The PDF files you want to combine
  • A free FileIO account (only needed to download the result)

Step 1 — Open the Merge PDF tool

Go to fileio.app/merge-pdf. No software to install, no account required to start.

Step 2 — Upload your PDF files

Click Click to browse or drag your PDF files directly onto the drop area. You can add up to 20 files at once. Each file can be up to 30 GB, though most documents are far smaller than that.

Tip: Upload all your files before clicking Merge — you can drag the list to reorder pages after uploading.

Step 3 — Reorder the files (optional)

The files appear in the order you uploaded them. Drag any row up or down to change the order they will appear in the merged PDF. The first file in the list becomes the first pages of the output.

Step 4 — Merge and download

Click Merge PDF. The tool combines your files server-side and the download button appears within seconds. Your original files are not modified.

Merge PDF files now — free

Tips for better results

  • Page order matters. Arrange files in the order you want before merging — reordering after is harder than getting it right before.
  • Reduce size first. If the merged file will be large, compress each PDF individually using the Compress PDF tool before merging.
  • Password-protected PDFs. Remove passwords first with the Unlock PDF tool — the merger cannot process locked files.

How to merge PDFs on iPhone or Android

Open fileio.app/merge-pdf in your phone's browser. Tap Click to browse and select your files from Files (iOS) or your file manager (Android). The steps are identical to desktop — no app to install.

Frequently asked questions

Is merging PDFs free?

Yes — the Merge PDF tool is completely free with no file size limit.

Can I merge more than two PDFs at once?

Yes — you can merge up to 20 PDF files in a single operation.

Are my files kept private?

Files are encrypted in transit with TLS and deleted from the server automatically after processing. They are never shared or used for any other purpose.