Really great experience. Entry to the cathedral is free anyway but this is included in the ticket price. You can buy on this app or at the grounds. There is an option for all monuments for €27 at the grounds depending what you want to do. I did this in January so it was busy but not overly crowded as I assume the hotter months would be! Still recommend this ticket if you want to plan your day in advance.

All smooth, no problem with the entry. However you need to first check your bags into the locker room about 150 metres from the tower entrance, so go there first. Then there is a small queue to enter the tower at your allotted time. The steps up aren't too steep - but on the way down they slope away from you and there is no handrail, so need to tread carefully.

We got there 15 minutes before our scheduled time but it wasn’t clear who to look for and where to go. Finally asked the people checking tickets to the Tower of Pisa and they said we can use the voucher bar code to get in. You also need to check your bag in a locker before going up the tower. Other than that, the climb was good and the view on top was great. We came early in the morning so it wasn’t too crowded yet (9-10Am). Suggest you do the same to avoid a crowded tower. The cathedral was beautiful too.