## Summary
* **What is the goal of this PR?** (e.g., Implements the new feature for
file uploading.)
Update "UI Font Size" to "Reader Font Size", to match the rest of the
"Reader" settings and clarify that the setting doesn't change the UI
font.
* **What changes are included?**
Changes the `english.yaml` string and USER_GUIDE.md entry.
## Additional Context
* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
specific areas to focus on).
---
### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _**< YES | PARTIALLY | NO
>**_
NO
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