How do I turn pages?

I have been using Libre for a while but now cannot find how to turn over the pages. One example has 56 pages showing but I am stuck on the first one, where is the button? Oh and what does tags mean?

So you used to be able to turn pages before and now you can’t. Something has changed. Questions abound. Have you done an update recently? What is your Operating System? Which version of LibreOffice are you using? What kind of document are you trying to view (odt, PDF, xls, docx)? Are all components of LO affected or just one (Writer, Calc, Presentation)? How exactly did you “turn pages” before this? Have you tried scrolling? Have you tried Page Up/Page Down?

Please Edit your question above to add the extra information.