Just hold down and then drag over the words you want to select, as you select part of a new word the whole characters in the word will be selected/highlighted.
If you prefer to select/highlight only part of a word (a group of characters inside a word), it would be easy to remove snap to start and/or snap to end:
Removing snap to start
Drag the pointer all over the first word and continues until the next word is also selected/highlighted, and then drag back to the first word.
Removing snap to end
Drag back after a new word is selected/highlighted, and then you are able to easily tune the end pointer.
Highlighting/text selection doesn't work on some documents
Creating a text markup annotation
Signing documents and saving signatures
Using full document text search
Converting handwriting to text
Changing the font of a text annotation