In order to make a custom copyright page:

  1. Go to the Book Info page (see left menu)
  2. Scroll down to the Copyright section
  3. Add whatever you like to the Copyright Notice section.

If you choose an All Rights Reserved license or do not select a license type, any content entered in the Copyright Notice section overrides the automatic copyright notice that Pressbooks creates. 

If you select a Creative Commons license, the custom notice will appear after the license text in both the webbook and your exports.

For more information on your copyright page in Pressbooks, check out https://guide.pressbooks.com/chapter/copyright-page/