Hello @HappyTeacher_63,
I hope you are doing well, and thanks for reaching out. We're sorry for the trouble you had.
Could you please share more details about the issue?
Which exact Acrobat Pro version and OS are you using (e.g., Windows 11 + Acrobat Pro 2026 build number)? Check from Menu > Help> About Adobe Acrobat.
Are you adding text via Edit PDF > Add Text or another tool, and is Open Sans Light installed on your system or only present in the PDF?
Can you please confirm if the original PDF has the font embedded (File > Properties > Fonts)?
Is it only specific to one PDF set, or with all the PDFs?
Please note that to edit text using a specific font, you must have that font installed on your computer. If the font isn't installed but is embedded in the PDF, you can only change the text's colour or size. The file and your "Let Adobe choose" setting are not the variables here. What changes from day to day is whether Open Sans Light is genuinely active on your system at the moment Acrobat launches. Acrobat treats a font as "available" for adding or editing text only if it is installed or activated on your operating system. A font that is merely embedded in the PDF lets you view it, and at most change colour or size, but it does not let you freely add new text. So the decision to substitute is made purely by whether the real font is present as a system font, not by anything in the document or the preference.
Open Sans Light is an Adobe Font, and Adobe Fonts are only present when a few conditions line up. The Creative Cloud desktop app must be running and signed in, and you must be online, or the fonts are "unavailable temporarily.
Acrobat only refreshes its font list when it launches. A font that activates mid-session will not register until you quit and reopen Acrobat. So the order in which the font is activated, and Acrobat is opened, can flip the result between days.
Creative Cloud periodically removes Adobe Fonts you have not used in a while, and they need to be reactivated for use in Acrobat.
So "yesterday" Open Sans Light was likely active when Acrobat started (no substitution), and "today" it was not, so Acrobat fell back to Minion Pro. Minion Pro is simply Acrobat's documented default fallback for Roman-script fonts.
On the preference: "Let Adobe choose" only decides which fallback font is used when a substitution is already necessary. It never decides whether substitution happens. That is why it can look like it works some days and not others; it is not the thing that is changing.
For more details, you can refer to these Adobe articles:
https://adobe.ly/458S7iE
https://adobe.ly/456jaeq
https://adobe.ly/3T42bXC
I hope this helps, and let us know if you need any assistance or have questions.
Regards,
Anand Sri.
AdChoices