Hi,
unfortunately it won't be possible to directly replace the Ghostscript version without updating PDFCreator Server first. We had to slightly modify PDFCreator Server in order to be compatible with Ghostscritp 9.25.
Most likely it will be possible to replace Ghostscript 9.25 with Ghostscript 9.26 in the current PDFCreator Server release, I will test it and let you know:
http://download.pdfforge.org/download/pdfcreator-server
If GS 9.26 works with the current PDFCreator Server release, we will probably supply an update containing it.
Best regards
Robin