Four different pwm using PIC 18f45k80
Section 19.4 of the datasheet discusses PWM operation. In reality, the PWM functionality uses only Timer 2. This timer controls the period (frequency) as explained by equation 19-1: 

PWM Period = [(PR2) + 1] • 4 • TOSC • (TMR2 Prescale Value)

Thus, so long as the frequency is common to all 4 outputs, you are all set there. Then, you can set each duty cycle independently using the CCPRxL and CCPxCON registers where x is equal to 1, 2, 3, or 4 depending on which duty cycle you want to set. Equation 19-2 explains how to calculate the duty cycle:

PWM Duty Cycle = (CCPR4L:CCP4CON&lt;5:4>) • TOSC • (TMR2 Prescale Value)

Now, when timer 2 equals one of the 10 bit values in CCPRxL and CCPxCON, that particular pin will toggle. Then, when timer 2 matches the value in PR2, all pins will toggle back to the original state.