Hello Ruben,
As a frequent visitor to the Adobe forums, and an occasional user of PageMaker myself, I know of a very few people for whom PageMaker works well under Classic. For me, it does work when everything in my computer is perfectly in shape, but have come to expect a major or minor disaster at any time. The necessity for frequent, and even serial backups is a vital one here.
If you like PageMaker and don't feel like spending more money in programs that may be oversized for your needs, I would suggest that you
1. Make a small partition in your HD (perhaps about 5 GB), and install a copy of OS 9.1 or higher (up to 9.2.2) and of PageMaker there. You would need to boot from that partition every time you want to use PageMaker. Or, if your HD is not large enough or you don't like the idea of partitioning it,
2. Get an old, cheap Mac and keep it exclusively for running non OS X applications. I kept my wife's old iBook 300 precisely for that; being a portable, it uses very little storage space. Plus, I can continue using my main Mac as usual.