Korean fonts are not rendered during document conversion

I have a file of extension dwg. It contains CAD basic fonts (whose extension is shx) included. When i convert the dwg to pdf using libreoffice, korean characters are not displayed. Instead of korean text, it is displayed as question mark.

I tried by installing korean language pack, but still the issue continues.

I tried the same file in other online viewers where they are displaying the korean fonts correctly.

Can you please let me know on how to resolve this issue?