Older PDF viewers or basic web browser preview tools frequently lack the complex character maps required to decode CID font families. 4. Faulty PDF Printers and Drivers

Open-source renderers like use CIDFont F1 Family as a default placeholder. When Ghostscript processes a PostScript file with a missing CJK font definition, it falls back to a built-in CID-keyed font. Inspecting the gs command line with -dFONTMAP often reveals:

If a PDF editor strips out font subsets to reduce file size (often called "downsampling" or "font optimization"), it may rename the remaining font dictionary to F1 Family because the original metadata is lost.

: If you have a PDF editor that allows you to edit text, you can select the garbled text and change its font to a standard one installed on your system, such as Arial, Times New Roman, or Calibri.