Pagemaker 7

I still cannot register. When I asked to register online, I am proposed 2 choices but the 1st one is greyed out.

The 2nd choice offers to print the registration, but doesn't let me print because I don't have a web browser installed

Pagemaker 7 was released YEARS before any Adobe apps had activation. You don't need to activate and it won't ask you. Registering is optional, and you don't need to. BUT you will need to enter your serial number when you install. Assuming that you can - it's a very big ask.

Released 2001 https://en.wikipedia.org/wiki/Adobe_PageMaker so you will not be able to activate

It may not even run on your operating system unless you have Windows XP or Mac OS 9.

How old is that program?

The activation server for CS3 (and earlier) has been removed... I know that CS5 was issued in 2010, so if your program was much before (say, 2 years?) that date it may be part of the activation server that was removed