In iOS 7, you have the ability to increase/decrease the font-size in all apps. There are basically two places where you can configure this feature and apps (that support “Dynamic Text Sizing”) will have larger/smaller text size based on your configuration.
This is usually an accessibility-related feature. If you find that text size is smaller in most of the apps that you are using, you should not strain your eyes. Instead, simply change the text size.
How to Increase Font-size On Your iPhone/iPad in iOS 7
- Open the Settings app
- Now, tap on General
- Tap on Text Size
- Draw the slider towards larger “A” to increase the font size. The font-size of the description represents (approximately) the way fonts will look on other apps and elsewhere on the iPhone/iPad.
There's also Accessibility where you can change the font size.
- Go to Settings → General
- Tap on Accessibility
- Tap on Larger Type
- You can draw the slider here to increase the font-size. You don't have to switch ON the Larger Dynamic Type switch. However, switching this on will give you “more” larger font-size options on the slider. In most cases, you don't need to switch ON this toggle but if you want a really big typeface, this is the switch to toggle.
Increasing font-legibility is not usually a necessity on iOS. Most of the apps designed for iPhones and iPads come with a design sense that makes reading easy. However, accessibility is a different thing. Also, dynamic type helps elders who need larger font-sizes to read legibly.
iOS 7 also lets you make the text “bold” system-wide. This option can be found in Settings → General → Accessibility → Bold Text. When you turn this on, the iPad needs to restart for the changes to take effect. (You will be asked if you wish to continue or cancel with the change).