Older PDF viewers lack the modern decoding engines required to parse CID (Character Identifier) font tables.
The designations like F1 through F6 are generic, temporary names assigned by the PDF generator. They often represent different weights (e.g., F1 for Regular, F2 for Bold) or entirely different font families used within that single document. Cidfont-f1 F2 F3 F4 F5 F6
The "F" numbers usually represent different of the same missing font: F1 : Often the "Regular" or "Bold" version. F2 : Often the "Italic" or "Regular" version. Older PDF viewers lack the modern decoding engines
Open the newly generated file to see if the text renders correctly. Step 3: Use an Alternative PDF Engine F1 for Regular