instead of showing numbers, the page numbers show a highlighted text with a words “page number” when editing a document. I wrote this document on LO Writer 5.1, and it was just fine then. This problem occurs when I open the document on LO Writer 5.2. Is there anyone can explain what happen and how to fix it?
You solve that with menu View - Field names or Ctrl+F9.
If this answer helped you, please vote it with 
(here on the left). That will help other people with the same question.
Thanks for your help.