They are standard font identifiers. However, always download font files from official sources (Adobe, Google, GitHub) to avoid malicious ZIP files.
Select and choose "Save as PDF" or "Microsoft Print to PDF" as the printer. Open the new saved file. The text should now be visible. 2. Use "Export as PDF" (Mac Users) cid font f1 f2 f3 f4 f5 f6 f7 fonts free download link
However, there are that your PDF will recognize as perfect substitutes. Below are the best resources. They are standard font identifiers
