To create a subpage, click the + under tabs but choose a different level--if the level is one less than top, it asks you to choose a top-level page to link it to. Choose the appropriate one and save.
I took an existing Word document and created a PDF version of it that has a password protection option, uploaded into the Library's Google Drive, and am linking it here. The password is Agronomy24. Since this is not a direct scan, I'm not sure yet if this is going to work for scanned book passages. More testing is needed. Please let me know if this works or not.
2nd test--this time this is a password protected PDF scan emailed to myself and uploaded into Google Drive. To open the file attached to the email, I did have to sign in using the password Knapp2023. That password should be needed to open the link here. And if this test is successful, we can scan segments of books, upload into Google docs, and link, locked down by a password you would have to share with students and/or their teachers to access. We can also use this technique to scan in other document types like articles.