Change radius for proportional editing When proportional editing is enabled in edit mode, then if you select and drag a point, nearby points will also move with it. The effect has a certain radius. How can you set this radius?
According to the documentation I found, you can set it using the scroll wheel or PgUp/PgDn. I tried those, but PgUp/PgDn seem to do nothing, and the scroll wheel instead zooms. What's the correct way to do it?
You must press PgUpPgDown or use the scroll wheel during a transform action such as Translate (G), Rotate (R), or Scale (S).
During a transform operation, you can see the proportional size visualized as as a circle around the Pivot point and you can see the actual proportional size value displayed in the Header:

In the Redo panel located at the bottom of the Tool Shelf (N in the 3D view) or found by pressing F6, there is a slider to adjust the Proportional size. Note that this only applies immediately after a transform operation.