A client has supplied a number of archival documents he would like converted to PDF.
The documents are Pagemaker 4.3.
Is there an InDesign plug-in that will open them? I have ID 1, ID 2, ID CS6, ID CC & ID CC 2014.
You can open up Pagemaker 5 or 6 in InDesign CS6.
Someone would have to find a working copy of Pagemaker 4 and convert to Pagemaker 5 or 6, then open in InDesign. I think your client is probably out of luck. It's just too old.
that's what I was afraid of
It's actually PM 6 or later. You'd need to get those PM 4 docs converted to PM 6 before you even consider anything else.
To do so you'd need PM 6 or later on the same platform that the PM4 document was created on since PM only allowed you open on a different platform OR a different version, but not both.
Perhaps try posting in the Pagemaker forum. There are still a few hardcore holdouts and perhaps one of them give you a hand.