Cari tanda tangan Text di file Pptx

        
// Set up input Pptx file
string filePath = "input.pptx";

// Instantiate Signature for input file
using (GroupDocs.Signature.Signature signature = new GroupDocs.Signature.Signature(filePath))
{
        //Create search options
        TextSearchOptions options = new TextSearchOptions()
        {
            // specify special pages to search on 
            AllPages = false,
            // single page number
            PageNumber = 1,
            // specify text match type
            MatchType = TextMatchType.Contains,
            // specify text pattern to search
            Text = "Text signature"
        };

        // search for Text signatures in Pptx document
        List<TextSignature> signatures = signature.Search<TextSignature>(options);

        // process signatures which were found                
        foreach (TextSignature item in signatures)
        {
            //...
        }
}