How It Works

Last updated: May 30, 2026

PDFMax is built on the open-source Stirling-PDF engine and runs in two distinct modes. Some tools process your files entirely inside your own browser and never upload them anywhere. Others use our processing engine, which works on your file in memory and discards it as soon as your session ends. This page explains exactly what happens to your documents.

Two ways your files are processed

Every tool on PDFMax falls into one of two categories. The tool page always tells you which mode applies, so you know up front whether your file leaves your device.

1. Client-side: processed entirely in your browser

Tools such as Compress and Split run fully on your device using WebAssembly. We load compiled engines like Ghostscript (for compression) and pdf.js (for reading and page handling) directly into your browser tab. When you select a file, it is read into your browser's memory and processed locally by that WebAssembly code.

• Your file is never uploaded to a server, not even temporarily.
• All computation happens on your own CPU, inside the browser sandbox.
• The result is generated locally and offered to you as a direct download.
• Once you close the tab, nothing remains anywhere but on your device.

Because there is no upload, client-side tools also work offline once the page has loaded, and processing speed depends on your own hardware rather than network conditions.

2. Server-side: processed in memory on our engine

Some advanced operations cannot run efficiently in the browser. Tools such as format conversion, OCR (making scanned documents searchable), and large merge jobs are handled by our processing engine on the server.

• Your file is sent over an encrypted HTTPS connection.
• The engine works on the document in memory and returns the result to you.
• Files are automatically deleted when your processing session ends. We do not keep them, mine them, or share them with third parties.
• We do not sell your data or use your documents to train models.

Security and privacy

All traffic to PDFMax is served over HTTPS with a strict referrer policy. Client-side tools keep your data on your machine by design, and server-side processing is short-lived and isolated. We collect no document content for analytics, and your files are not accessible to anyone outside the transient processing session.

Supported formats

PDFMax works with the document and image formats people use every day:

• PDF — compress, split, merge, rotate, OCR, and more.
• Office documents — DOCX and other common office files for conversion to and from PDF.
• Images — JPG, PNG, and similar formats for conversion and assembly into PDFs.

Quick guides

How to compress a PDF

• Open the Compress tool and add your PDF.
• Choose a quality level; the file is compressed in your browser.
• Download the smaller file directly to your device.

How to merge PDFs

• Open the Merge tool and add two or more files.
• Drag the pages or files into the order you want.
• Run the merge and download the combined PDF.

How to convert a file

• Open the relevant conversion tool and add your document or image.
• The file is processed securely over HTTPS by our engine.
• Download the converted result; the source file is then discarded.

Questions?

If you want more detail about how a specific tool handles your data, contact us at support@pdfmax.app. To report a security concern, write to security@pdfmax.app.