How do I enlarge fine print for better readability?

You can experiment with the Display panel in System Settings/Preferences to alter the text presentation, or you can see an optometrist to have your eyes tested and a "computer" eyeglass prescription that will allow finer print legibility at typical screen viewing distance. That is what I use with the small text on my 4K display and it works quite well.

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We're not clairvoyant so you'll have to be more specific.

What system are you running?

What text do you want larger, i.e. menus, menu bar at top, in apps?

fishdetector (Author)

Perhaps if only simple issues affect use of an application

window, not an entire macOS interface; there usually are

separate controls inside a Browser (text or menu) to help.

Sometimes the macOS displays Control can adjust the

entire system/font, but other undesired effects result.

Subtle adjustments may be available through 3rd Pty

software; or display maker may have custom version.

Various macOS (older Mac X / 9 etc) w/ different tools

offered variable choices; according to Software apps.

And certain software offered proprietary tools as well.

Sorry to not offer anything surprising or exceptional.

it's a bit too vague what it is that you are asking

do you want bigger fonts?

do you wish to zoom in on an image but it makes text fussy?

do you something else?