[yawaramin]

WhatsApp fetches a link preview on the sender's device before the message is encrypted, and packages it up with the message before sending. Depending on how exactly they implement the fetch, they may or may not know what links you sent.

[Sami_Lehtinen]

At least links in PDF over WA didn't get visited from FB servers. I just personally tested it moments ago.

[Thorrez]

What's visiting the links? Your phone?