https://www.jetbrains.com/help/pycharm/zooming-in-the-editor.html

To enable changing font size in the editor

1. Open the Settings/Preferences dialog, expand the Editor node, and click General.
2. Make sure that the setting Change font size (Zoom) with Ctrl+MouseWheel is enabled.

To change font size using the mouse wheel

1. Place the caret in the editor.
2. While keeping the Ctrl/? key pressed, rotate the mouse wheel. As you rotate the mouse wheel forward, font size grows larger; as you rotate the mouse wheel backwards, font size decreases.

   The macOS users can use trackpad "Pinch-to-Zoom" gesture to change size of the font and the whole editing area.

pycharm Zooming in the Editor