Scanning, PDF and TIFF imports have been permanently removed from modern versions of Finale. You may have recognized this as SmartScore Lite Scan in previous versions of Finale.
As we were developing Finale (Version 25), our first 64-bit version, we had announced plans to augment the scanning features in Finale to include a PDF importer. This spurred a larger conversation within the publishing and composing community about the security of copyrighted content. You can read more details about our decision in the following blog post: Restrictions May Apply*.
It's clear to us that removing this feature was painful for many users. Thankfully, there are some other options! Our friends at Musitek offer some affordable options, including a smartphone app and desktop app, which offer both scanning and PDF import capabilities, as well as a MusicXML exporter that can send files to Finale. While the need for additional software isn't ideal, these are definitely good options if you rely on scanning as part of your workflow.