No, you do not have to be a pledge member to purchase. But as a new member, sellers may require more info from you before they will be willing to sell to you.
You do have to be a pledge member to post in the classified forums, including the want-to-buy forum.
◄▀▄▀▄▀ NEW RULE - You must be a pledge member to post, 5 MAX listings/bumps. ▀▄▀▄▀►
The link in the post above is out of date. Go to the Rolex Discussion forum and use the 2022 Pledge Member thread at the top of that forum.