I am trying to find a way to save the current page in a multi-page pdf, so that when I re-open the document, it opens to the same page? I read somewhere that you can change the preferences to allow this, but I can't find the preferences.
You can find it at Edit > Preferences
I can't even find an "Edit" tab to click on.
What version of Acrobat Reader does you use? What is your OS?
Edit is not a tab, it's a menu (top of window in Windows; top of screen in Mac).
If there are no menus, but you are on Mac or Windows, perhaps you are using the obsolete Acrobat Reader Touch; if so, get to Acrobat Reader DC http://get.adobe.com/reader (it will look VERY different). If you're on iOS or Android, I doubt it can be done.
If you're using a Mac it's not under Edit but under the Reader app menu, or you can use Cmd+K to open it directly.
There is a preference "Restore Last View Settings When Reopening Documents:" which should help you
Hopes it helps