Hi Isaac,
Sorry for the delay in response.
As you have mentioned above, you cannot write the Korean memo on the PDF.
Adobe Acrobat Reader mobile application is free software that helps you to view PDFs on the mobile device.
It also helps you to annotate, print and share the PDFs on your mobile device.
Could you please let us know how exactly you are trying to add the memo in the PDF?
Are you using the comment tool in the application to make the changes on the PDF?
It would be helpful if you can share the complete workflow you follow to add the Korean Memo on the PDF.
We will be waiting for your response
Let us know if you have any questions.
Regards,
Meenakshi