I am working on a UK-based site - but we have customers all over the world, including Russia. However, when customers enter their address using the non-latin Russian / Cyrillic alphabet, there are missing characters on the PDF invoice. I expect it's something to do with UTF-8. Is there a way to show these missing Cyrillic / Russian characters?
A solution I implemented is the string transliteration.
We ported the nice transliteration extension from Drupal and made it work on Magento for PDF printing and logistics data exchange.
To transliterate strings means that characters are converted to US-ASCII.
That's a solution that may or may not suit your needs, because the data becomes different from the original.