SketchPad Explorer

Sketchpad Explorer was a free app for the iPad that is no longer available that used to allow you to view and interact with Sketchpad documents, called sketches.

Once a sketch is open in Sketchpad Explorer, you will be able to drag objects and select buttons just like you would in Sketchpad.
In addition, there are three buttons at the bottom right of the screen.
Three buttons at the bottom right of the screen

They allow you to get information about the app, temporarily magnify a region of the sketch and access saved and sample sketches respectively.
You can transfer sketches using File Sharing in iTunes, using email attachments, using links in web pages or using services like Dropbox (see the link below for more details).

Use two fingers to pan and zoom a sketch.

The webpage, http://www.dynamicgeometry.com/General_Resources/Sketchpad_Explorer_for_iPad.html, outlines the various features of the app. Among the cooler features is the ability to: