The only way to produce version 6 (.pm6) of Adobe PageMaker from version 5 files (.pm5) would be to use any version of the program above 6 and simply re-save the files. No other way how to do it, as the support for PageMaker formats in other programs is pretty limited, or rather nonexistent.
Convert Adobe PageMaker 5 document file to Adobe PageMaker document.
We found one software available in the database for this conversion.
Microsoft Windows software - convert pm5 to pm6 on Windows
One of the first desktop publishing programs on market
Convert from pm5 file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.