1- Adobe Ideas
Adobe® Ideas gives you the ability to draw freeform vector illustrations wherever you are. Replace your pen and paper with a huge virtual canvas, customizable brushes, and pressure sensitive stylus support. With a Creative Cloud membership, easily sync Adobe Ideas projects to Creative Cloud and open them for refinement in Illustrator2- Air Sketch
Air Sketch is great for presentations in the boardroom, classroom, or on the go. Just fire up Air Sketch on the iPad and open the specified URL from any HTML-5 compatible browser on the local network. Your photos and drawings show up natively in the browser. There's no additional client software to install, or services to subscribe to.
Brushes is a painting app designed exclusively for the iPhone, iPod touch, and iPad. Rewritten from the ground up, Brushes 3 is universal — the same version runs on both your iPhone and your iPad. Move paintings between your devices and keep working wherever you go!
4- Sketchbook Pro
Autodesk SketchBook® Pro for iPad is a professional-grade paint and drawing application. Using the same paint engine as its desktop counterpart, SketchBook Pro delivers a complete set of sketching & painting tools through a streamlined and intuitive user interface designed exclusively for the iPad experience.