Q: When I open a PDF document in Korean (or Chinese, Japanese Respectively), , the bookmarks entries in Korean font are displayed as undefined characters under the Bookmarks pane. I am running in Windows 10.

Before installing Korean language pack, the Korean characters show as undefined
Undefined Korean Characters under Bookmarks

A: You will need to add the Korean font pack to Windows 10.

Read more on Microsoft website.

  • Go to Start > Settings
  • Type in Languages
  • Select¬† Time & Language
  • Click Add a Language Button
  • Add Korean (or Japanese / Chinese Respectively).
  • Make sure to reboot / restart your machine
After installing Korean Language Pack, bookmarks display correctly with Korean font