Grain Offset Scripts for Corel Painter 7 and above are a collection of macro scripts which can be used to offset the current paper texture overlay position prior to any mark being made on the canvas or layer. Currently, the only way I know to do this without using scripts is to apply texture in smaller, selective areas on individual layers and then reposition these areas using the Layer Adjuster tool. You can then erase any areas of unwanted texture to fit the region you wish to overlay.
In Painter 11 and earlier versions, the paper texture preview may be dragged around in the Paper Preview Window of the Papers palette, but unfortunately this has no effect on the texture overlay position when it is applied to the canvas or layer.
The individual scripts generally move the pre-applied paper texture by a preset number of pixels in a given direction, but a user defined script has also been included such that the Row Origin and Column Origin values for the offset can be manually edited prior to running the script. Also included is a script to reset the grain position to the default origin. The scripts can either be ran via. the Play button in the Scripts palette, or via. a custom palette (shown below) in the case of the presets.
Tutorial and download link.