UTF-8 allows for support of various languages, including Asian languages and their character depth. It is a widely supported and flexible character encoding, used for many European languages and can also represent Chinese, Japanese and Korean.
It's fairly simple to enable UTF-8 on your wiki pages. Currently PmWiki 2.0 versions have the UTF-8 file needed already loaded.
If you validate your site you should see that UTF-8 is default encoding.
See also Cookbook:UTF-8 for tips.