Websites promising a free download of "Cid Font F3" are usually phishing hubs or distribution networks for malware, adware, and trojans.
When you see this error, your first action should not be a desperate web search for a "CID Font F1 free download." Instead, you should assess your goal. Do you simply need to read or print the PDF? The "Print to PDF" or "Export via Preview" solution is your quickest path forward. Do you need to edit the text? Open the PDF's properties to identify the missing font and install a suitable replacement. Are you building a document from scratch? Use one of the legitimately free font archives or tools mentioned above, and be sure to embed your fonts. Cid Font F1 F2 F3 F4 F5 Free Download
Older PDF readers struggle with unenclosed or unembedded CID fonts. Modern web browsers and advanced readers have built-in global character engines. Websites promising a free download of "Cid Font