Your Historical Timeline page is a customized blog page, where each blog post is a point on the timeline.
The year for an entry on the timeline is set by the publish date of each blog post. The headline text for each entry on the timeline is set by the headline field for each post. The optional descriptive text for each entry on the timeline is set by the "Before the flip" content for a post.
If any of your timeline posts include content "after the flip", a Read more button will show up in the timeline entry for that post that users can click to read the full description.
The downloadable PDF version can be replaced by uploading a new file named "Historical_Timeline.pdf" under the Files tab for your Historical Timeline page in your NationBuilder Control Panel.