Dave, sorry about that. That one is the full upgrade not the update.
This is the update.
It may or may not do it.
The problem is that with no disks you cannot become the owner of any of that software nor the Mac itself.
That is something that people do not know or do not say when selling a computer and including third party software.
They keep the disks because they want the software, they are selling only part of the software. It really does not matter what the software is if it requires a serial number.
In effect you are not the owner of that Mac as far as the Mac is concerned, it still belongs to the seller.
You may be able to change ownership by changing who has permission but it is a slim hope.
Open Applications and right click Pro Tools. Select Get Info from the menu.
Give yourself Read/Write and close it, repair permissions.
If it has an Apply to enclosed folders, check it. Then you only need do this once.
That is why I wipe all used Macs so that this does not happen, without the installation disks including any serial numbers that software is like a used car with sawdust in the transmission. It will go for a time before it quits.
You are not the owner of that Mac even though you bought it and have you as the only user. The seller is still owner of record as far as the Mac cares.
The only way to become the owner is to wipe and erase the hard drive and start fresh. Then you become the owner.
That is the best I can do. I have dealt with this same thing myself and speak from experience.