How to Remove Watermark from PDF using C#. For more details: https://kb.conholdate.com/total/net/how-to-remove-watermark-from-pdf-using-csharp/

how-to-remove-watermark-from-pdf-using-csharp.cs

using System;
using System.Collections.Generic;
using Aspose.Pdf;
namespace AsposeProjects
{
    class Program
    {
        static void Main(string[] args) // Main function to remove watermark in C#
        {
            // Initialize license
            License lic = new License();
            lic.SetLicense("Aspose.Total.lic");

            // Load the source PDF file with a watermark on it
            Document document = new Document("watermark.pdf");

            // Instantiate a list to save the watermark-type artifacts
            List<Artifact> artifactsToBeDeleted = new List<Artifact>();

            // Parse through all the pages of the loaded PDF file
            foreach (var page in document.Pages)
            {
                // Parse through all the artifacts in the current page
                foreach (var item in page.Artifacts)
                {
                    // Check if the type of the current artifact is a watermark
                    if (item.Subtype == Artifact.ArtifactSubtype.Watermark)
                    {
                        // Save the artifact reference in the list for later deletion
                        artifactsToBeDeleted.Add(item);
                    }
                }
                // Parse through all the artifacts to be deleted
                foreach (var item in artifactsToBeDeleted)
                {
                    // Delete the current artifact
                    page.Artifacts.Delete(item);
                }
            }

            // Save the resultant PDF file having no watermark in it
            document.Save("withoutWatermark.pdf");

            Console.WriteLine("Done");
        }
    }
}