Notes · 2026-08-23

What "free" actually costs

"Free" tells you what you pay, not how the thing survives. Software costs money to build and keep working, so something is funding it. Being able to name that something is the single most useful skill for judging whether an app will still be there, unchanged, in three years.

Who wrote this: Mantra Factory. We sell a paid app, AddToPDF, so we have an obvious interest in making free software sound risky. We have tried hard not to: two of the six models below produce software we recommend over our own, by name, and the last section is about when you should not pay us or anyone else.

This is not an argument against free software

Some of the best software ever written is free. Apple's Preview is free, and for most PDF tasks it is the correct answer. Skim is free, open source, and better at annotating academic papers than any paid app we know of. PDFgear is free and does things our paid app does not.

The argument is narrower: "free" is not one thing. It covers at least six arrangements with wildly different consequences, and the differences only become visible later — when the app is acquired, or adds an account, or quietly stops working after an OS update. Sorting them out in advance takes about a minute.

The six models

1. The loss-leader

Free because it makes something else more valuable. Preview is free because Apple sells Macs. A good bundled PDF viewer makes the hardware better, so Apple funds it.

What it means for you: stable, as long as the platform still benefits. The risk is not disappearance but neglect — features you want may never arrive, because the product's job is to be adequate, not excellent. Preview has been "nearly able to do that" for about a decade.

2. The public good

Free because someone maintains it for a community they belong to, usually with open source. Skim is the example here: researchers maintaining a tool for researchers.

What it means for you: the best durability story of the six, for one reason — the source is available. If maintainers lose interest, the code does not evaporate; someone else can pick it up. The real risk is a slow stall rather than a sudden shutdown, and compatibility drifting after OS releases.

3. The free tier

Free because it is advertising for the paid version. The free tier is deliberately shaped so that the thing you eventually need sits just past the wall — page limits, watermarks, a locked export.

What it means for you: honest enough when the wall is clearly marked, infuriating when you discover it after twenty minutes of work. Check where the boundary is before starting anything long.

4. Your data or attention

Free because you are what is being sold — behavioural data, an email address to market to, ads.

What it means for you: mostly a concern for web and mobile rather than desktop utilities, but the question to ask is simple: why does this need an account? A tool that edits a file on your own disk has no technical reason to know who you are. When it insists, that is information.

5. Bundled installers

Free because the installer carries something else — a toolbar, a "system optimiser", a changed default search engine. This is the model that gave free PDF readers their reputation two decades ago.

What it means for you: the one genuinely adversarial category. The tells are an installer with several screens of pre-ticked checkboxes, a download that arrives via a "download manager" rather than the file itself, and a website with several competing green buttons.

6. Unfunded goodwill

Free because one person made it, solved their own problem, and released it. No company, no revenue, no plan.

What it means for you: often superb, and the most fragile. Nothing is wrong with the software; there is simply nothing obliging anyone to update it when the OS changes. If the source is public it becomes model 2 and is far safer. If it is a closed binary from a personal site last touched four years ago, treat it as borrowed time.

How to tell which one you have, in about a minute

Name the revenue. Say out loud how this product pays for itself. If you cannot finish the sentence, that is the finding — not proof of anything sinister, just genuine uncertainty about its future.
Look for the company, and ask what it sells. A hardware maker, a paid tier, an enterprise product, an ad network — each points at a different model above.
Ask why it wants an account. For a tool that edits a local file, there is usually no technical reason.
Check whether the source is available. This is the single strongest durability signal, because it decouples the software's survival from any one person's enthusiasm.
Watch the installer. Pre-ticked extras are the clearest red flag in this entire list.
Find out where the file is processed. Local, or uploaded to a server? This is not about price at all, and it matters more than price for anything confidential.

The axis people forget

Cloud versus local is a completely separate question from free versus paid, and for sensitive documents it is the more important one. A paid browser service still uploads your contract to someone else's machine. A free desktop app may never touch the network. Do not let the price tag answer the privacy question.

When free is simply the right answer

We would rather say this plainly than have you buy something you did not need:

Signing a document, or annotating one, on a Mac? Preview. Free, installed, and it does this well.
Reading and marking up academic papers? Skim. Better than the paid options for that job.
Need real PDF editing or OCR without spending anything? PDFgear. It does things our paid app does not.

Our comparison of Mac PDF editors works through all of them, including where each beats us.

So what is paying actually for?

Not features, necessarily — a free tool may have more. What a small one-time price buys is a named, boring reason for the software to keep existing and stay the same. Someone is paid to make it work on the next OS version. It has no incentive to add an account, because it is not being funded by knowing who you are. It will not acquire a subscription later, because it is not a funnel toward one.

That is a modest thing to sell. It is also, for a tool you will still want in three years, most of what actually matters.

And to hold ourselves to the same test we just proposed: AddToPDF is model zero — you pay for it, once, and that is the entire business model. There is no free tier funnel, no account, and no network connection at all. If we ever add one, you would be right to ask which of the six we had moved into.

AddToPDF — the app we make

A deliberately small PDF editor for Mac, iPhone and iPad: add text, sign, fill forms, organise pages. Fully offline, no account, one-time purchase covering all three devices. It does not edit existing body text or do OCR.

Download on the App Store

Frequently asked questions

Is free PDF software safe to use?

It depends entirely on which free it is. Software bundled with your operating system, such as Apple's Preview, and established open-source projects are generally as safe as anything you pay for. The categories that warrant caution are installers that bundle extra software, tools that require an account for a task that needs no account, and browser-based services that upload your document to a server in order to process it. The test is whether you can identify why the product is free.

Why is some software free?

There are six common reasons: it is a loss-leader that makes a platform or hardware more valuable; it is genuinely maintained as a public good, usually open source; it is a free tier advertising a paid one; it is funded by collecting and selling data or attention; it is funded by bundling other software into the installer; or it is unfunded goodwill from someone who simply made it. Each has very different implications for whether the app will still exist and behave the same way in three years.

Is open-source software more trustworthy than paid software?

On one specific axis, yes: the source can be inspected, and if the maintainers stop, someone else can continue from the code. That is a real durability advantage. It does not automatically mean better security or better maintenance, since inspection only helps if someone actually does it, and unfunded projects can and do stall.

What is the catch with free online PDF tools?

The main one is architectural rather than commercial: browser-based tools upload your document to a server in order to process it. For a public document that is unimportant. For a signed contract, an identity document or a medical form, it means handing personal data to a third party, which in some professions carries obligations of its own.

Should I pay for software that has a free alternative?

Often, no. If Apple's Preview signs your document, use Preview. Pay when you need something the free option genuinely cannot do, or when you need a specific guarantee — that it will still exist, still behave identically, and still be supported in a few years — and the price is small enough that it is not really a decision.