The only way, how old *.ald4 files from some version of PageMaker for Mac could be converted to PDF is to do it in the program, because Pagemaker formats are not supported in any other programs.
Convert Adobe Pagemaker 4 for Mac file to Adobe Portable document format.
We found one software available in the database for this conversion.
Apple macOS / Mac OS X software - convert ald4 to pdf on OS X
Mac version of once popular publishing program
Convert from ald4 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.