You can assign any digital pin to any LCD input, but you must make sure that the correct pins are matched to the LCD pins in the constructor. Just to clarify this a bit:
All of the I/O pins on the Arduino are digital, including the so called 'analog' pins.
Most of the signal pins on the LCD are I/O, only the RS and E are input only.
You can use any available Arduino I/O pin to connect to any of the LCD signal pins.
//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12); // put your pin numbers here