Note that this is currently a Beta feature. If you don't see the "Copy to another locale" button in your documents, you can request early access to this feature from the chat support in your Prismic repository or on the prismic.io website.
If you have set up your repository to use multiple languages, you will have to produce documents for the different locales. You can create an alternative language document from scratch, but you might find it more efficient to copy the content or content structure of the original language document over to this new document. Without having to reproduce the fields, slices, and media content used, you can focus instead on translating the text itself.
The 'Copy to another locale' button
Once you have configured two or more languages in your Prismic repository, you will notice some new elements in your Writing Room interface. The Copy to another locale option will open a pop-up that allows you to specify what you wish to do with the document you have currently open, as well as the target locale.
Copy all content
As you might expect, this option will duplicate every single bit of content to your target locale. Text, links, media content as well as any slices used and their layout will be copied over. This is particularly useful when you intend to use a consistent experience for your users, as well as facilitating the job of those in charge of translating your content. It will allow them to work directly on top of the original text instead of copying it over manually or having to keep multiple browser windows open.
Copy slice structure and assets
If you prefer, you can duplicate only the slices used, their layout, as well as Media Library assets you have in the original document. This means that all text fields will be left empty and waiting for their translated content. You might prefer this option if you wish to start from scratch when working on a different locale, but without having to configure the slice layout all over again in each new document.
Prismic provides a simple workflow for working alongside your translators. After producing and saving a new document in any language, you'll notice the To Translate tags used to notify translators that there are documents awaiting to be translated. You can then copy the content of your original document to those target locales, so they can be used as the basis for the translators to work with. These localized documents should be then saved and published, either immediately or as part of a release.
Hope you find this Prismic feature both useful and efficient, with fewer steps between content production and publishing it to a wider audience.