PageMaker 6.5 plug in
There should be an optional plug in for importing PageMaker files into newer (than CS6) versions.
I am in the same situation. With the upcoming Catalina upgrade on Mac, which will not support CS6, I will lose years of work.
As Adobe have now withdrawn InDesign CS6 there is no way to edit and update Pagemaker files. Having been a user for about 25 years, I have a portfolio of hundreds of client files which go back to pre InDesign days. Many of these are book publications that from time to time need to be edited and updated. Currently I have a backlog of more than thirty which need to be accessed for editing and republication. I am faced with hundreds of hours work to reset these jobs without a means to open .p65 and .pmd files.