Open the problematic file in a browser like Firefox or a native app like macOS Preview . Choose Print > Save as PDF . This process often flattens the fonts or substitutes them with system defaults, making the text readable again.
Open the file in Preview and use File > Export as PDF . This sometimes "flattens" the font information into a usable format. cid font f1 f2 f3 free download high quality
If your workflow specifically requires files named f1.otf , f2.otf , f3.otf , those are often custom-named internal company fonts. In such cases: Open the problematic file in a browser like