How to access a local/custom windows service (openoffice) from IIS 7.5 without assigning local system rights to the application pool

How to access a local/custom windows service (openoffice) from IIS 7.5
without assigning local system rights to the application pool

We have created a delphi ISAPI webservice on IIS 7.5 which needs to access
the openoffice service to open a document and save it in an other format.
The web service can create/generate the odt file but for saving it in an
other format I need to use the openoffice com interface to open the
generated document and save it in pdf and doc format. Is there any
"secure" way to do so? Now when I try to call the openoffice service it
tells my that the access is denied!