A common mistake we've all made, particularly as new users, is to forget where we are and do an entire layout on a master page. The next time you open the document it will open to a regular document page and all content will appear locked because it is all on the master page.
If that's what's causing your problem, the best solution, in my opinion, is to go back to the master page and select all of the objects that don't belong there, then cut to the clipboard. "Paste in Place" on the live page. If you've used layers, open the Layers Panel flyout menu and enable "Paste Remembers Layers" before pasting.
Peter
