Method 1: From the top annotation toolbar
1. Tap the Annotation Toolbar icon on the Action Bar. If you don't see the Action Bar, tap the center of your screen to bring it up.
2. Tap one of the text markup tools: the Highlight tool, the Strikeout tool, or the Underline tool.
3. Tap and drag on the text you want to markup.
Method 2: From the quick tools menu
1. Tap and hold on the text you want to markup until the quick tools menu pops up.
2. Tap the text markup tool you want to use. You can hold and drag the selection handles to adjust your text selection.
Signing documents and saving signatures
Using full document text search
Using Stylus as Pen mode
Converting handwriting to text
Enabling continuous annotation mode
Highlighting/text selection doesn't work on some documents