This article explains how to highlight text in Pages, including how to leave notes once you've highlighted something. Pages allows you to highlight text so a specific section stands out from the rest ...

PopClip adds a popover menu whenever you select text on Mac. This makes it easy to access basic actions such as cut, copy, and paste, and it has many extensions to send text to third-party apps ...

Clicking and dragging is a perfectly good way to select text, but there are others, possibly better, ways to go about it.