As said, it is well worth it. Very easy.
My husband kept saying "get us signed up" years ago.
But, out of sight, out of mind, I didn't know the process, thought it might be scary.
Finally one day after flying home, he steered us into the Pre-Check office at the airport. Of course we didn't have the necessary documents, but they gave us the web site information, told us how it would work, etc.
Went to the web site, got the info, signed up for an appointment time.
You do the web for each person, and based on your answers it tells you the documents you'll need to bring to get signed up.
Got our documents together.
Walked in, nobody else there so we got through it all in about 15 minutes.
Next day or so we both received e-mails with our KTN (Known Traveler Number), and also got letters with same.
Documents: Everybody needs picture ID and Birth Certificate.
I needed those plus copy of marriage license since that resulted in my name change.
That's all.
Note: An article in our paper yesterday said that after all the recent publicity, the Pre-Check sign up has gotten 'backed-up' in some major areas as there was a rush of people signing up, and they had not staffed the offices to accommodate. Sound familiar? So, do make an appointment. Those with appointments get priority over walk-ins who do not.