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PDF Master Lab
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PDF tools that never upload your files

Merge, split, compress and convert PDFs in seconds. Everything happens inside your browser — your documents never leave your device.

Merge PDFs nowSee all tools

Your files never leave your device

All processing happens in your browser. Nothing is transmitted to a server.

  • Nothing is uploaded

    Your PDFs stay on your device. Processing uses WebAssembly and JavaScript that run only in your browser tab.

  • No waiting in a queue

    There is no server queue. Your computer does the work locally, so you start right away.

  • Free, with no sign-up

    Every tool is free. No account, no watermarks, no daily caps. We fund the site with affiliate links and ads.

Frequently asked questions

Are my PDF files uploaded to a server?
No. Every tool on PDF Master Lab runs entirely in your browser using WebAssembly and JavaScript libraries. Your files are read and processed inside the current tab. Nothing is transmitted to our servers, and we never receive, store or see the documents you open.
Is PDF Master Lab really free?
Yes. All four tools are free to use with no account, no watermarks and no usage limits. We never charge you for processing. The site is funded by affiliate recommendations and display advertising, so the tools themselves stay free for everyone.
Do I need to install software or create an account?
No installation and no sign-up. Open the tool page in a recent Chrome, Edge, Firefox or Safari browser with JavaScript enabled, add your PDF, and download the result. Preferences for theme and language are saved only in your browser’s localStorage.
What is the maximum file size?
Each PDF can be up to 100MB. Because processing happens on your device, very large or complex files may still be limited by your browser’s available memory. If you hit a memory error, try splitting the document first or closing other heavy tabs.
Does it work on phones and tablets?
Yes, on recent mobile browsers that support modern JavaScript. Smaller files work well. Large multi-page PDFs are usually faster on a desktop or laptop because they have more memory and processing power available in the browser tab.