When the SketchBook app finally came out in September 2009, Cheung, 40, and Heermann, 47, hoped to get 100,000 downloads in a year. They got one million in 50 days.

The basic version of Autodesk's SketchBook app has been in the Play Store for a long time, but now the professional version has come to Android. Autodesk SketchBook has more advanced tools, a ton ...

Autodesk SketchBook users can now access all of the app's features for free, opening up a whole set of previously-premium features for everyone.