Local PDF tool - browser processing

Merge PDFs offline in your browser

Combine several PDFs into one local output with reorder controls, page ranges, optional section dividers, and a print-shop cover sheet.

Merge PDFs locally See the proof

0 bytes sent proof

What the widget measures

The panel counts what leaves your browser after you choose a file. The site's own scripts and fonts load like any web page — what you will never see is a request carrying your PDF. Check it here, or open your browser's Network tab and see for yourself.

0 bytes of your document sentStarts measuring when you choose a file on a tool page
Document request bodies
0 bytes
App network after file open
0 bytes
Processing engine
Browser WASM worker

The number is scoped to request bodies after you choose a document. App assets such as JavaScript, WASM, and fonts can still load; those are not your PDF bytes.

Verify it yourself
  1. Open DevTools, then the Network tab.
  2. Choose a PDF in the tool and complete the action.
  3. Filter for fetch or XHR requests; document processing should not create a request carrying your file.

Stronger check: load the tool page first, then disconnect from the network before choosing the file. Already-loaded tool code can continue processing locally, but a first visit still needs the site assets.

Steps

How to do it in Lemmafour

  1. Choose Merge PDFs locally.
  2. Use Add PDFs or Choose PDF to select one or more PDFs.
  3. Drag cards or use Move earlier and Move later to set the order.
  4. Open file options if you only need selected page ranges.
  5. Set output options if needed, then choose Merge PDFs and Download.

Expert note

Offline wording precision

Being precise about "offline": the first visit needs the internet, because the page and its PDF engine have to load like any website. After that, the engine is already in your browser — you can switch on airplane mode, choose your PDFs, and the merge still works. Try it.

FAQ

Questions people ask before using this tool

Can I merge only certain pages?

Yes. Open file options for a PDF and apply page ranges before merging.

Can I reorder files?

Yes. Use drag and drop or the move buttons on each file card.

Will I see network requests in DevTools?

Yes — the app itself (scripts, fonts) loads like any website. What you will not see is any request carrying your PDF. That is the part to check.

Related private PDF workflows

Keep working locally

Merge contract PDFs without uploading Combine contracts, exhibits, schedules, and signature pages locally in your browser. Split a PDF without uploading Split one PDF into several local output files in your browser without sending the document to a server. Organize PDF pages offline Reorder, rotate, duplicate, delete, and insert blank pages locally in your browser. Compress a PDF locally Reduce PDF file size right in your browser — the file never goes to a server to be compressed. PDF tool hub Browse the shipped local PDF tools.