The "F1" tag (along with F2, F3, etc.) is a assigned by PDF creation software. When a program like Microsoft Word or Adobe InDesign exports a PDF, it may rename the embedded fonts to generic tags like "F1" to maintain a small file size or handle font subsets.
If you see "CIDFont+F1" in your document properties, it means the software has assigned a temporary name to a font to ensure it displays correctly across different platforms, especially for large character sets like Chinese, Japanese, or Korean (CJK). The Technical Mystery cid font f1 family