existing wordpress website in multiple languages

I have an existing word press website in English language. I want to make a copy of the website in another language. I do not need auto translation as I can enter contents separately. Is there a plugin for this? Or do I need to have one more wordpress site / subdomain?

There are two ways to go:

WPML or plugin way

WPML or any translation plugin, but personally I find WPML the best option, even though it's not free. The plugin handles everything, string translation, language switcher, page duplication, permalinks etc.

There is also qTranslate, and some others that I've not used.

WPML is the easiest and the best one to use (imo).

WPMU (Wordpress Multi Site)

Other option is creating a multisite (WPMU). Basically you copy the entire wordpress site (and the database), and paste the site to a subfolder on your server that has the name of the translation (if you want German translation you create a de folder).

Then using Search Replace DB script, replace old links in the database with the new ones (matching the folder). And now when you go to www.yoursite.com/de you'll have the same wordpress as the original one, and you can set this one as a German one.

The linking between the two is more tricky since you have to do everything manually (language switcher etc.).

WPMU is lighter on the database then the WPML since you have two separate installations, databases etc. but is less 'automatic'. If you create a post on one wp (English), you'll need to go to the other wp and create it in German. Whereas on WPML there is a duplicate button, so you can just duplicate the page/post etc. and translate it with ease.

Also wpmls 'String Translation' plugin makes it very easy to translate any translatable string inside the theme or plugin you are using. You don't need to pull the .po files, translate them and then paste them back with language code at the end. Wpml does this for you withing the backend.

My opinion: WPML all the way, it's easy and pretty straightforward. Easier for someone who doesn't have that many experience with database transfers etc.