is not a specific, downloadable commercial font but rather a generic font substitution name or encoding method used by software (like Adobe InDesign or various PDF generators) when an original font was not properly embedded .
Avoid shady "font download" websites promising cidfont_f1normal.zip . In 2021, these are 90% malware, adware, or fake driver updaters. There is no legitimate F1Normal file.
Because "CIDFont F1" is a unique identifier generated by the software that created the PDF, there is no official "CIDFont F1" file on the internet. If you are getting a "missing font" error, it means the PDF was created without the font data, and your computer cannot find the original font (like Arial) that F1 is supposed to represent. CIDFont+F1 issue - Adobe Community