Problem with Permalinks on Pages

I am creating a website in wordpress (not a blog) and I am having problems with my permalinks. I tried to change them to post name but that came up with error 404 everytime I clicked on a link. I have since found out you are better to put a numeric value in the links too.

I am trying to create a custom link of
/%post_id%/%postname%/
this works fine on posts but on pages just displays ‘domainname/postname’ therefore giving me error 404. I have tried replacing %post_id% with %page_id% but this makes no difference.

Can anyone help?