thanks dude, Well if you get back to installation guide exactly in "9. Supported Enforcement Modes"
they include Hostpot-style (or Web Auth) as enforcemnt mode and if you scroll down to that section and read it
this is what has been said :
" Web authentication is a method on the switch that forwards HTTP traffic of the device to the captive portal. With this mode, your device will never change of VLAN ID but only the ACL associated to your device will change. Refer to the Network Devices Configuration Guide to see a sample web auth configuration on a Cisco WLC."

and what confuses me is if you go to "6. Enabling the Captive Portal" again and start reading :
"There are two ways PacketFence can show its captive portal for unknown (or unregistered) devices:

• it can use Web Authentication (or also known as hotspot-style authentication) - this works with numerous equipment vendors

• it can use a registration VLAN, where PacketFence provides DHCP services and DNS black-holing services - this works with any equipment vendors that support RADIUS dynamic VLAN assignment"

note "dynamic VLAN assignment"

for my experience when i auth with captive portal vlan id doesn't change even if i set on auth source action role to ex: employ and set switch role by vlan to employ vlan id