Eliminate vanishing pencil lines while drawing (Illustrator CS/CS2/CS3/CS4)

If you’ve ever created an illustration with the Pencil tool you’ve most likely noticed every time you draw a path next to an already selected path, the original line disappears as soon as you draw the next line. Why? Because the Pencil tool defaults to path-editing mode. This means that when you draw a line near a selected previous line, Illustrator assumes you want to edit the previous line, so it deletes the line and replaces it with the new line. Annoying, right? Don’t worry—you can change this behavior.

To do so:

1. Double-click on the Pencil tool to open the Pencil Tool Preferences dialog box.
2. Deselect the Edit Selected Paths check box or reduce the pixel distance using the slider at the bottom and click OK.