import com.spire.pdf.FileFormat;
import com.spire.pdf.PdfDocument;
import com.spire.pdf.PdfPageBase;
import com.spire.pdf.general.find.PdfTextFind;
import com.spire.pdf.general.find.TextFindParameter;

import java.awt.*;
import java.util.EnumSet;

public class PdfFindAndHighlightDemo {

    public void findAndHighlight(String pdfFiles, String keyText, Color highlightColor){

        String outputFile = "output.pdf";
        PdfDocument pdf=new PdfDocument();
        pdf.loadFromFile(pdfFiles);
        PdfTextFind[] result = null;
        for (Object pageObj : pdf.getPages()) {
            PdfPageBase page = (PdfPageBase) pageObj;
            // Find text
            result = page.findText(keyText, EnumSet.of(TextFindParameter.None)).getFinds();
            if (result != null) {
                for (PdfTextFind find : result) {
                    find.applyHighLight(highlightColor);
                }
            }
        }
        pdf.saveToFile(outputFile, FileFormat.PDF);
        pdf.close();

    }
}

using Spire.Pdf;
using Spire.Pdf.General.Find;
using System.Drawing;

namespace DemoOnlineCode
{
    class FindAndHighlightDemo
    {
        public void findAndHighlight(string pdfFiles, string keyText, Color highlightColor)
        {

            string outputFile = "output.pdf";
            PdfDocument pdf = new PdfDocument();
            pdf.LoadFromFile(pdfFiles);
            PdfTextFind[] result = null;
            foreach (PdfPageBase page in pdf.Pages)
            {
                // Find text
                result = page.FindText(keyText, TextFindParameter.None).Finds;
                if (result != null)
                {
                    foreach (PdfTextFind find in result)
                    {
                        find.ApplyHighLight(highlightColor);
                    }
                }
            }
            pdf.SaveToFile(outputFile, FileFormat.PDF);
            pdf.Close();

        }
    }
}