Add a QR Code to a PDF

The code is generated locally — no request to a QR service, which matters because the thing you are encoding is often a link nobody else needs to know about. It is drawn as vector squares rather than an image, so it stays crisp at any print size and adds almost nothing to the file. Higher error correction makes the code denser but lets it survive damage, a fold or a logo printed over it.

Is anything sent to a QR service?

No. The code is generated in your browser from the text you type.

Which error correction should I use?

Medium is right for most things. Use the highest level if the code will be printed on something that gets handled.

It will not scan. Why?

Usually too small, or printed on textured paper. Test one before a print run.