Traditional Spiritual Symbolism:
The rungs on a ladder represent levels in a hierarchy, and so can symbolise levels of spiritual awareness. A ladder may indicate communication between levels, or ascension to a higher spiritual plane. The symbolism of the ladder used in a metaphysical or 'spiritual' context is linked with the Great Chain of Being, reflecting levels of order in the world and the universe, from the lowest orders of nature to the heavens and God. The ladder can refer to the Κλίμαξ, Climax Paradisi or Scala, "The Ladder of Divine Ascent" upon which ordered steps the faithful achieve perfection.
Some think that drawing doodles of ladders may indicate ambition and a desire to succeed, whether it is the corporate ladder you are climbing, or some other personal or professional goal. A firmly-drawn and regular ladder might suggest a firm resolve, while a shaky and uncertain ladder may indicate uncertainty. Got your ladder set against a wall? Perhaps you see obstacles in your way but you also have the means to surmount them.
Renovating? Ladder doodles might be inspired by their use somewhere in your environment, or possibly an experience with them in your past. Perhaps you own a ladder-back chair, or have played snakes-and-ladders lately?