Does Apple have a free pdf editor?

You can create a document in Pages, save it as both a Pages file and a PDF. Edit the Pages document and resave it with the changes as a PDF. Otherwise, no.

You can create a document in any app and print it to pdf, that's an option in the Print Dialogue. Or, as dialabrain suggests, some apps ahve an export to pdf option. Preview can edit pdf documents in a limited fashion, but it might work for your usage.

For documents you create the previous suggestions are an excellent way to go. However, for PDF file you get from other sources not so. You'll need a PDF editor app. If you search the App Store for PDF you'll get a number of options, some free with in app purchases. I use PDF Expert which i got in a bundle of apps at a ridiculously low price. Now, not so much.

It's different matter altogether if you have an existing PDF document that you want to edit. You cannot load an existing PDF into Pages and edit it. PDF documents can also be password protected and editing locked by the author of the document. For that you would need either Acrobat or other PDF editor.