Extending a line with the Pen Tool
After you have finished drawing a line you can extend it at any time. You can use any of line drawing tools (Freehand & Brush Tool, Pen Tool, Shape Editor Tool). As the Pen Tool has limited functionality, you may find the Shape Editor Tool easier to use.
To extend a line with the Pen Tool
1. Select the line (see Selecting objects).
2. Click on the end point handle to extend from (the Shape Editor Tool or Selector Tool can be used for this).
3. Choose the Pen Tool.
4. Now click or drag as normal (see Drawing a Line with the Pen Tool) to add the new line section.