Clicking on the online share link to a report will always show the most up to date version in your account. When generating a PDF it'll save a copy from the time you create it and won't update automatically if you make any edits or changes to the report later on.

In the Share menu you'll see a note to let you know changes have been made to a book after the last PDF was created:

If you'd like to generate a new copy click on create up-to-date PDF. Alternatively you can continue to use the last version. You'll know if the PDF is up to date as we won't show you a link to the previous version.