How to mark up a PDF with PDFelement? You can go to the "Comment" tab to find the text markup tools, you will see "Highlight", "Area Highlight", “Pencil", “Eraser", “Underline", and many other tools there for your quick access. Holding the Alt key, or holding the mouse button, allows you to select a region of text to work with.
If you want to change the color of the text markups, please select the markups you make, then right-click the highlight or underline to choose "Properties". In the right-side Properties panel, you can change the color and opacity in "Appearance" options.