Code to Find and Replace Text in PDF using Java. Here is linked article: https://kb.aspose.com/pdf/java/how-to-find-and-replace-text-in-pdf-using-java/

How to Find and Replace Text in PDF using Java.java

import com.aspose.pdf.Document;
import com.aspose.pdf.License;

public class FindAndReplaceTextInPdfUsingJava {

	public static void main(String[] args) throws Exception {

		// Instantiate license to create presentation in HTML
		License pdfLicense = new License(); 
		pdfLicense.setLicense("Aspose.Pdf.lic");

		// Load the input PDF document
		Document pdfDocument = new Document("Input.pdf");

		// Create TextFragmentAbsorber object
		com.aspose.pdf.TextFragmentAbsorber textFragmentAbsorber = new com.aspose.pdf.TextFragmentAbsorber("Rack");

		// Set text replace options
		com.aspose.pdf.TextReplaceOptions options = new com.aspose.pdf.TextReplaceOptions();
		options.setReplaceScope(com.aspose.pdf.TextReplaceOptions.Scope.REPLACE_FIRST);
		textFragmentAbsorber.setTextReplaceOptions(options);

		// Accept the text absorber for the entire collection of pages
		pdfDocument.getPages().accept(textFragmentAbsorber);

		// Get the extracted fragments in a collection
		com.aspose.pdf.TextFragmentCollection textFragmentCollection = textFragmentAbsorber.getTextFragments();

		// Loop through all text fragments
		for (com.aspose.pdf.TextFragment textFragment : textFragmentCollection) {
			// Update the text
			textFragment.setText("New Rack");
		}

		// Save the updated PDF file
		pdfDocument.save("Output.pdf");
		
		System.out.println("Done");
	}
}