I have already applied for a green card but now I want to apply for travel document and work permit while my application is pending. Do I have to pay extra to be able to receive work permit or advance parole since I already filed my I-485?

The filing fees for the I-485 adjustment of status include the filing fees for both work and travel authorization. Even if you have already filed the I-485, you can submit the applications for work and travel authorization at any time without an additional fee. Just be sure to provide proof of your pending I-485 in the form of a copy of your receipt notice with your applications.