SearchWatermarkInParticularObjectsAllInstances.cs

// For complete examples and data files, please go to https://github.com/groupdocs-watermark/GroupDocs.Watermark-for-.NET
Document.DefaultSearchableObjects = new SearchableObjects
{
    WordsSearchableObjects = WordsSearchableObjects.Hyperlinks | WordsSearchableObjects.Text,
    CellsSearchableObjects = CellsSearchableObjects.HeadersFooters,
    SlidesSearchableObjects = SlidesSearchableObjects.SlidesBackgrounds | SlidesSearchableObjects.Shapes,
    DiagramSearchableObjects = DiagramSearchableObjects.None,
    PdfSearchableObjects = PdfSearchableObjects.All
};

foreach (var file in Directory.GetFiles(@"D:\files"))
{
    using (var doc = Document.Load(file))
    {
        var watermarks = doc.FindWatermarks();

        // The code for working with found watermarks goes here.
    }
}