Why are spool files, which are printed to a physical printer are getting so large?

Behavior:
While doing a further print to a physical printer via the DocuWare Printer, the spool file which is send to the physical printer becames quite large. 

Solution:
Since the DocuWare version 6.5 we print the documents as image, this leads to the described behavior. To reduce the size of the spool file, the number of DPI has to be reduced on the physical printer, for example to 300 or 200 dpi.