It depends on how the page is set up, but there are pages that don't allow users to edit except for those with the authorization.
To display/save a page to PDF, click PDF button at the top of the page.
You can do the same with the get PDF button at the bottom of the page.
To see a page's edit history, click the history button at the bottom of the page.
All incremental changes on a Wiki page are saved, so you can browse all the edit history.
You can also go back to the previous version.
To delete a page, click the delete button at the bottom of the page.
To set a page to allow only specific users to edit/browse, click the config button at the bottom of the page.
For each category of users, like project admin, editor, project member, login user, all anonymous, you can set up the range of authorization to all operation/editing(creating)/view only/none.