It might be possible that old Adobe PageMaker could export *.add files as a PDF documents. However this information could not be verified.
Convert Adobe PageMaker related file to Adobe Portable document format.
We found 2 software records in the database related to .add to .pdf file format conversion.
Microsoft Windows software - convert add to pdf on Windows
One of the first desktop publishing programs on market
Convert from add file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned add to pdf. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert add to pdf on OS X
Mac version of once popular publishing program