Can customers add custom messages with products in an app?

[cassen45]

I want to give customers the ability to write a custom message that comes with the product. Is there an app for that or do I have to look somewhere else?

[PaulNewton]

There are plenty of apps that do things like this , search for "product personalization" in the app store.

Though be aware this may be accomplished either with theme setting or a one time theme customization.

Typically this can be handled by turning on cart notes for a theme , for vintage themes see the following help doc

https://help.shopify.com/en/manual/online-store/themes/themes-by-shopify/vintage-themes/customizing-... 

For advanced customizations

For product level info https://community.shopify.com/c/shopify-design/product-pages-get-customization-information-for-produ...

For cart level info 

https://community.shopify.com/c/shopify-design/cart-use-cart-attributes-to-collect-more-information/... 

In online store 2.0 compatable themes the info customization may be possible in product forums with custom-liquid blocks