Error trying to sign a document

Hi,


When I try to sign a document, I get the following:
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PDFCreator - www.pdfforge.org
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Errorprotocol
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PDFCreator 1.7.0 - Error message
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ERROR DESCRIPTION:
          Error-Nr: -2147024894 (Can’t load file or l’assembly ‘itextsharp, Version=5.2.1.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca’ o una delle relative dipendenze. Can’t find the specified file.)
          Modul: modGhostScript
          Procedure: CallGScript
          Line:      50710
          Date/Time: 06-14-2013 / 15:44:34
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CALLSTACK:
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SYSTEMINFO:
 Windows XP
  [5.1 Build 2600 (Service Pack 3)]
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