Because "F1" is just a label (often representing the first missing font found in the document), it could be mapping to anything from to Times New Roman depending on the specific file. How to Fix the CIDFont+F1 Error

The font CIDFont+F1 is Arial (blod) and CIDFont+F2 is Arial (Regular) CIDFont+F1 issue - Adobe Community

Google Fonts : Excellent for web-safe and universally compatible fonts like or Open Sans .

Adobe Fonts : If you have a Creative Cloud subscription, using is a common recommendation to replace missing CID fonts. CID+ Fonts - Adobe Community