Problema compatibilitate office 2010 – cu versiuni de office mai vechi: http://technet.microsoft.com/en-us/library/cc545900.aspx
Office 2010, just as the 2007 Office system, uses the XML-DSig format for digital signatures. In addition, Office 2010 has added support for XAdES (XML Advanced Electronic Signatures). XAdES is a set of tiered extensions to XML-DSig, the levels of which build upon the previous to provide more reliable digital signatures. For more information about the levels of XAdES that are supported in Office 2010, see Using digital signatures later in this article. For more information about the details of XAdES, see the specification for XML Advanced Electronic Signatures (XAdES) at: http://go.microsoft.com/fwlink/?LinkId=186631
It is important to be aware that digital signatures created in Office 2010 are incompatible with versions of Microsoft Office earlier than the 2007 Office system. For example, if a document is signed by using an application in Office 2010 or in the 2007 Office system and opened by using an application in Microsoft Office 2003 that has the Office Compatibility Pack installed, the user will be informed that the document was signed by a newer version of Microsoft Office and the digital signature will be lost.
The following figure shows a warning that the digital signature is removed when the document is opened in an earlier version of Office.
Also, if XAdES is used for the digital signature in Office 2010, the digital signature would not be compatible with the 2007 Office system unless you configure the Group Policy setting, Do not include XAdES reference object in the manifest, and set it to Disabled. For more information about the digital signature Group Policy settings, see: Configure digital signatures later in this article.
If you need digital signatures created in Office 2010 to be compatible with Office 2003 and earlier versions, you can configure the Group Policy setting, Legacy format signatures, and set it to Enabled. This Group Policy setting is located under User ConfigurationAdministrative Templates(ADMADMX)Microsoft Office 2010Signing. After this setting is set to Enabled, the Office 2010 applications use the Office 2003 binary format to apply digital signatures to Office 97–2003 binary documents created in Office 2010.”