Does this change the pages?

No. Only the outline is removed.

Why would bookmarks be wrong?

Usually because pages were added or removed after the outline was written.

organize

Remove PDF Bookmarks

Strip the sidebar outline from a document.

Runs in your browser

How it works

Removes the outline entirely. Worth doing when an outline has been inherited from a source document and now points at the wrong places, which is more useful than leaving a navigation aid that sends readers to the wrong page.

Related tools

Add Bookmarks

/add-bookmarks-to-pdf

View PDF Bookmarks

/view-pdf-bookmarks

Remove PDF Annotations

/remove-pdf-annotations

Questions

Does this change the pages?: No. Only the outline is removed.
Why would bookmarks be wrong?: Usually because pages were added or removed after the outline was written.
Can I rebuild them?: Yes, with Add Bookmarks.