Hi Stephan and welcome to the forum.
I am not sure it they would be of any help to you but the Generic/Text Only printer does have some advanced proporties that, by name at least, seem to suggest they may do something interesting that might be relevant to your problem - like what to do with the file after printing and such things (from memory).
Have you experimented to see it any of the options does anything at all to help? I'm wondering if one of them might function by adding version numbering to the default file name. In which case I would guess that each file would spool independently without overwriting.
Alternatively does the report creation program have an option that can be changed to prevent it writing separate files for each page?