Documents lets you highlight, underline, and strikethrough PDF texts with different colors. This is a great way to interact with a document actively and emphasize its key points.

1. Open a document.
2. Tap Annotate on the toolbar.
3. Select the Highlight   , Underline  , or Strikeout  tool. You can select the color for each tool by tapping the color picker  .
4. Select the text to annotate it.
5. To remove the annotation, long tap the text and select Clear in a pop-up menu.

There is an alternative way to mark up text in PDFs:

1. Tap and hold on the text you want to annotate.
2. In a pop-up menu, select Highlight, Underline, or Strikeout. On iPhone, use the arrows to find the needed option.
3. To change the color, tap the annotated text and select Color in a pop-up menu.
4. To remove an annotation, tap Clear in a pop-up menu.
5. To undo the changes, tap  on the toolbar. If you need to redo your edits, tap and hold and select Redo.