How to make pages/word documents open in preview first?

If you do a right click on this file, but before that you can hold down the Option key and click “Always open with”. Then just select Preview.

If all you want to do is see the contents of the file, no need to open it at all. Just use Quick Look. Select the file and the hit the spacebar to view the contents.

Documentation

View and edit files with Quick Look on Mac

Quick Look offers a fast, full-size preview of nearly any kind of file without opening the file. You can rotate photos, trim audio and video clips, and use Markup—directly in the Quick Look window.

On your Mac, select one or more items, then press the Space bar. A Quick Look window opens. If you selected multiple items, the first item is shown.

• Browse items (if you selected multiple items): Click the arrows near the top-left of the window or press the Left Arrow or Right Arrow key. In full screen, click the Play button to view the items as a slideshow.
• Show items in a grid (if you selected multiple items): Click the
  Index Sheet button or press Command-Return.
• Open an item: Click Open with [App].
• Share an item: Click the Share button , then choose how you want to share the item.

When you’re done, press the Space bar or click the Close button to close the Quick Look window.