Missing fonts in Adobe Illustrator are the result of not having a font which the artwork uses; already installed on your computer.
Opening a file without the correct fonts installed (or without converting the text to outlines) will yield the error displayed below in Fig 1.
Adobe Illustrator will prompt you to choose a substitute font that is installed on your computer.
Fig. 1 - Missing Fonts Error
Show me the Fonts
Your computer uses the fonts held under it's own file system, typically found in Windows here: C:\Windows\Fonts
(or by pressing Windows Key + R and entering shell:fonts in the Run dialog)
Mac users: simply open Font Book in a Spotlight search.
New fonts can easily be installed onto your computer; and are widely available in the following formats:
TTF - True Type Format
Developed by Apple in the late 1980s
OTF - OpenType Font
Developed by Microsoft and Adobe Systems in the Mid-1990s
You can Download Fig. 1 as our example:
Download Here
Sorting it Out
There are three options to resolve this issue:
1. Sync the missing font with Adobe
As you are using Adobe Illustrator, you may have a subscription to Adobe Cloud but not have Adobe Acrobat Pro.
Therefore, we recommend you try to sync the missing font if available via https://fonts.adobe.com/
2. Download and install the missing font
You'll certainly find a reputable font merchant by using your favourite search engine.
3. Convert the text to outlines
This will yield a Vector conversion of the text; to Points and Paths.
Meaning you cannot type text in the same font; but as such, you can avoid the requirement of having to purchase a potentially expensive font.
Let's Convert Text to Outlines
Load the File
Open the file in Adobe Acrobat.
You'll be prompted to verify the security of your document.
Why verify?
PDF readers (as all softwares) are programs written by humans, and one or more vulnerabilities may be present within their codebase.
Much like many food products may contain nuts or milk.
Malicious code is often injected into files; and vulnerabilites within the codebase of a program provide the platform for hackers to execute otherwise forbidden instructions to your computer. By skirting the rules of the program it's interacting with; the malicious code of a hacker can inject spyware, ransomware, trojans, viruses, worms and other unwanted programs onto your computer.
"That which one may do, another may equally undo."
If you know your file contains no malicious data; go ahead and continue.
Preflight
Once the artwork is loaded into Adobe Acrobat, look toward the right side of your screen for the Search tools section.
Type Preflight .
Then click Select to select it.
Convert
You'll then be greeted with the Preflight window, follow the steps below:
1. Ensure Essentials is selected (as highlighted in red).
2. Navigate to the Find section and type Outline.
3. Select Convert fonts to outlines.
4. Click Analyze and fix, located in the bottom right corner.
Save
You will now be prompted to save the file in PDF format (under the same file name).
BEWARE - If your source file is PDF, you might overwrite the existing file.
It's Done
The PDF file you just saved; now has the missing fonts included as Vector elements.
You'll be able to adjust the size, colour and shape of the font in your favourite Vector editing suite.