Now for the most important part: how do you actually get rid of these warnings and keep your fonts looking the way you intended?
In a perfect world, the missing font would be embedded. But when embedding fails or is disabled, the system resorts to : swapping your chosen typeface with a default one (like Courier or Arial) without your explicit permission. Download Font Substitution Will Occur
Some designers use "subset embedding" to reduce file size. This includes only the specific characters used in the document (e.g., only the letters A, B, C if those were typed). If the printer needs a character not included in the subset—say, an em dash or a special symbol—the system will warn that a substitution will occur for the missing characters. Now for the most important part: how do
If you frequently face this warning, request that senders save files as PDF/A-1b (an ISO standard for archiving). PDF/A requires all fonts to be embedded and forbids substitution. If a file complies with PDF/A, the warning will never appear. Some designers use "subset embedding" to reduce file size