creates a new, perfectly readable file with the fonts properly mapped Check Document Properties: In Adobe Acrobat, press (Windows) or (Mac) and go to the tab to see the actual font name that "F1" is supposed to be Manual Substitution:
After installing one, configure your PDF software to map /F1 to, e.g., NotoSansCJK-Regular .
To summarize, here is your step-by-step checklist to resolve this issue today:
After installation, test your setup with a known problematic PDF.