You can use the Highlight Text tool, Strikethrough Text tool, and the Underline Text tool to mark up text in MobiOffice PDF.
1. Open a PDF in MobiOffice.
2. Switch to the Review tab.
3. Select your option: Highlight, Strikethrough, or Underline.
4. Drag over text to perform the action.
You can also change the color
To do that, tap Color and pick or create a custom one from the expandable bottom sheet.