Tryouts available here
Adobe - PageMaker : For Windows
But be warned that pagemaker will not work in anything later than windows XP. There is lots of discussion on this issue in other threads. It will not install on newer macs.
Adobe Customer service is getting really lazy.
Scratch that the link doesn't work, sorry.
AFAIK, there are no functional trials available for PM.
IIRC correctly, there was no such thing as an upgrade disc. The upgrade was really the full installation with your Licence Number proving you had an earlier version and entitling you to a discount.
So, taking in consideration all the constraints above and the fact PM is totally obsolete and wholly unsupported, all you need to install PM7 is your Licence Number.