PDF tools that don't upload your files, and how to check

Two ways an online PDF tool can work

Server processing. You choose a file, it's uploaded to the company's computers, the work is done there, and you download the result. Reputable services delete files after a while, often between one and a few hours, but for that time a copy of your document sits on someone else's system.

In-browser processing. The website sends your browser the code needed to do the job. Your browser then opens the file and makes the new PDF itself, on your device. The document is never sent anywhere, so there's nothing to store or delete.

Modern browsers are powerful enough to merge, split, compress, convert, sign and even read scanned text this way. Every tool on PDF ProMaster works like this.

Why it matters

• Private paperwork. Payslips, bank statements, tax returns, passports, contracts and medical letters often contain exactly the details fraudsters look for.
• Work documents. If you handle other people's personal data, such as clients' or patients', uploading it to a third-party website may go against your organisation's data protection rules.
• Speed. No upload and download means large files are often faster, especially on a slow connection.

How to check whether a PDF site uploads your files

1. Read its privacy page. Look for wording such as "files are deleted after one hour". That tells you they're stored on a server for that long. "Processed in your browser" or "never uploaded" means the opposite, as long as it applies to every tool.
2. Try airplane mode. Open the tool and let the page load fully, then turn off Wi-Fi or switch on airplane mode. Add your file and run the tool. If it still works, the file is being processed on your device. If it stalls or shows a connection error, it needed a server.
3. Watch the network (on a computer). In Chrome or Edge, press F12 and open the Network tab, then run the tool. If you see a large request about the size of your file going out, it was uploaded.
4. Watch for mixed approaches. Some sites process light jobs in the browser but send heavier ones, such as Office conversions or OCR, to a server. Check the specific tool you plan to use.

The trade-offs of in-browser tools

Being honest about the limits helps you choose:

• Very large files depend on your device's memory. A phone may struggle with a 300-page scan that a laptop handles easily.
• Some conversions, such as PowerPoint to PDF, are much harder to do well in a browser, which is why PDF ProMaster doesn't offer them yet. Excel to PDF works, but doesn't include charts or pictures yet.
• The first use of a heavier tool, such as OCR PDF, downloads its engine first, which takes a moment.

Free PDF tools that never upload your files

Every PDF ProMaster tool runs in your browser:

• Organize: Merge PDF, Split PDF, Extract pages, Delete pages, Organize PDF and Rotate PDF
• Convert: Word to PDF, Excel to PDF, PDF to Word, JPG to PDF, PDF to JPG, OCR PDF, Image to Text and Text to PDF
• Edit: Edit PDF, Compress PDF, Sign PDF, Watermark PDF, Add page numbers, Crop PDF and Compare PDF
• Security: Protect PDF and Unlock PDF
• All in one: the PDF ProMaster Workspace

Comparing options? See how PDF ProMaster compares as an iLovePDF alternative and a Smallpdf alternative.

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