High DPI devices, such as 1920x1080 resolution displays require some sort of intervention from the operating system to prevent "ordinary" text from becoming painfully small.
The root cause of the problems is how this is done, and whether the way it does so accomodates legacy programs.
For any application that has the problem, right click the executable > Properties > Compatibility tab > uncheck disable scaling for High DPI devices.
That should do it.
An excellent explanation for why is given in this article by The Windows Club:
"Blurry Fonts or Text in Windows 8"
Below is a more global approach that gets you a fix fast across everything. You can then go back and fine-tune when you have time.
On Windows 8, turning off the option "Smooth edges of screen fonts" in the Visual Effects dialog box improves the situation.
Win+R > control > in search box type: visual > System: Adjust the appearance & performance of windows > Visual effects tab > UNCHECK "Smooth edges of screen fonts".
You can see BEFORE and AFTER images below. Computer: Lenovo Ultrabook laptop running Windows 8.1 with a 1920x1080 display. Application: legacy desktop application R Statistical Computing Platform.