Thanks for reporting this.
I found two separate issues here:
The JPY currency symbol used by SubTotal was the full-width yen character (¥). Some bundled PDF fonts do not support that glyph, so I changed it to the standard yen symbol (¥). This should fix the missing currency symbol.
The bundled PDF fonts currently do not include Japanese glyphs. Because of that, Japanese invoice text or Japanese layout labels may disappear in exported PDFs unless a Japanese-capable custom font is used.
SubTotal already supports custom PDF fonts in “My company”, so uploading a compatible TTF font there, e.g. Noto Sans JP, should solve the Japanese text rendering issue without increasing the app size for all users.
I also added a warning for future versions when the PDF contains characters that the bundled fonts may not support.