Are there any extensions that will enable a customer to enter their own text for a personal message in different types of fonts? For example, the customer is buying a gift and wants a personal message, and can choose what font it's printed in.
Products can have custom options. Here you can read about it: https://docs.magento.com/m2/ce/user_guide/catalog/settings-advanced-custom-options.html
The short answer is "yes".
Thanks Damian. I've read the link you suggested but I can't find any information about being able to change the font for the message. Is that possible?
Maybe your fon options could be another custom option for the product.
I guess you'll find at least 2 levels of solutions here:
You will find several examples (even some module into the https://marketplace.magento.com/) but it will depend with the level of effort you want or need to apply.
I think the easiest way is using custom options to set product persoanl options (you can have more than 1 option per product but using too many maybe can be hard to manage)
(my 2 cents)