If you are using Word 2016 or Word 2013 and want to display the number of words at the top of the page then you can follow the below mentioned steps.
Step 1: Navigate to the first page in the document and click the Insert Menu.
Step 2: In the Insert menu, navigate to Text section and click Quick Parts option.
Step 3: Select the Field from the Quick Parts drop down list.
Step 4: In the Field window, choose the filed name as NumWords, Format 1,2,3 and Numeric Format 0. Click OK button to confirm and save the changes.
This would display the total number of words in the current document. In case you have made any changes to the document after adding word count field then to know latest count, right click on inserted filed and select Update Field from the list.