Is it safe to upload a PDF to an online tool?

What happens when you upload a file

When you drop a PDF onto a typical online tool, your browser sends the whole file over the internet to the company's servers. The work happens there, a copy is kept for a short while so you can download the result, and then it is deleted. The big names say so on their own pages. iLovePDF says processed files are deleted within two hours. Smallpdf says it deletes files after one hour.

Those are specific promises, and we are not claiming either company breaks them. The catch is what happens in the meantime. For an hour or two, a copy of your document sits on a machine you do not control, run by people you have never met. You are trusting a policy, not something you can check.

When it does not matter

Plenty of PDFs are not secret. A conference schedule, a public report, a recipe you want to shrink for a phone. If you would be fine pinning the file to a notice board, upload it anywhere and move on.

When it does matter

Think twice before uploading any of these:

• A contract that has not been signed yet.
• Anything with an ID number, an account number or a home address on it.
• Medical, legal or HR documents.
• Files a client or employer asked you to keep confidential.

The last one is often a formal rule. If you handle other people's data for work, sending it to a third party's server may break your company's policy or a contract, whatever the tool says about deleting it. Check before you upload, not after.

A different way to do the same job

The alternative is a tool that does the work on your own computer. The page loads in your browser, the program runs there, and your file is read from your disk and written back to it without being sent anywhere. PDFLocal works this way. You can merge, compress and redact a PDF without the document ever leaving the browser tab. The page does make a few small requests, such as counting how many free runs you have left today, but none of them contains your file.

You do not have to take our word for it. You can check any tool yourself, ours included, and it takes a few minutes.

What you give up

Doing the work in the browser has costs. Your own computer does the processing, so a very large file on an old laptop will be slower than it would be on a server. There are no accounts, so nothing follows you from one device to another. For everyday jobs such as joining, splitting, compressing or locking a PDF, a current browser is plenty.

If you want a short rule, ask this before you upload: if this file leaked next year, would I mind? If the answer is yes, keep it on your device.