Word documents with custom page size are converted in default size
By default, PDFCreator only knows the paper formats that are created when it is installed. If a custom format is defined in Word, PDFCreator does not recognize it and thus Word will use the default page size.
To create new paper formats, they have to be created under Print Management->Server settings. There you can create name and dimensions of the format. Afterwards, you can use it in Word.