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Aspose.Cells for Python via .NET provides the Workbook.add_digital_signature method that you can use to add digital signature to an already signed Excel file.
The following sample code demonstrated how to make use of Workbook.add_digital_signature method to add digital signature to already signed Excel file. Please check the sample Excel file used in this code. This file is already digitally signed. Please check the output Excel file generated by the code. We have used the demo certificate named AsposeDemo.pfx in this code which has a password aspose. The screenshot shows the effect of the sample code on the sample Excel file after execution.

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