- Right-click the dimension to be changed, and select Edit Model Dimension from the menu.
- Enter the new dimension in the edit box.
- To change the dimension tolerances, click the flyout in the edit box, and select
Tolerance...
Note: To turn off the ability to edit model dimensions from the drawing go to
Tools tab 
Options panel Application Options
Drawing tab and deselect
Enable part modification from within drawings.
Options panel Application Options
Drawing tab and deselect
Enable part modification from within drawings.