There are several ways to scale patterns in Illustrator. This post and the video tutorial below will outline some of the differences and advantages of each.
Just like in Photoshop, scaling in Illustrator falls under the term Transform. Other transformations that can be applied to objects in Illustrator are Rotation, Reflect, and Sheer.
The typical method for scaling patterns in Illustrator is through the scale tool settings. First, apply a pattern fill to an object, then double click the scale tool on the toolbar to open the tool dialog box. You can now choose to only transform the pattern fill by un-checking Object, and checking Pattern in the dialog box. This way, you can scale your pattern by entering a percentage to make it larger or smaller within your object.
You can similarly change the rotation and the shear for your pattern fill by double clicking on the corresponding tool in the toolbar, un-checking Object and checking Pattern to only transform your pattern within your shape.
Each subsequent object you draw will contain the rotated or scaled pattern fill. To restore the pattern fill to it’s original scaling and rotation, simply select the object and click the pattern fill swatch to reapply the pattern fill.
In Preferences > General (command/control K) you’ll find a checkbox for Transform Pattern Tiles. Uncheck this box to maintain the original scaling and orientation of a pattern fill as you resize and rotate objects.
The Illustrator tutorial above shows the basic method for scaling patterns in Illustrator, along with an alternate method using the tilde (~) key. To utilize this extremely useful shortcut, choose any of the transform tools: Select, Scale, Rotate, Reflect or Shear, and hold down the tilde (~) key while dragging the mouse. This allows you to manually transform your pattern within your object without transforming the object itself. This technique bypasses the dialog boxes that are discussed in the first method. Using Shift with the tilde (~) key allows you to constrain proportions while scaling your pattern.