When a PDF is exported with "subsetting" enabled, the software might assign generic names like F1, F2, or F3 to different weights or styles (e.g., F1 for Bold, F2 for Regular).
Since you cannot "download" these specific fonts, you should use these workarounds to view or edit your document:
Since you cannot download "F1" or "F2" directly, you must resolve the error by identifying the original font or re-embedding the data. 1. Identify the Real Font