Add And Search Hidden Text In PDF File

In this tutorial, we will walk you through how to add and search hidden text in PDF file using Aspose.PDF for .NET. Follow these steps to perform this operation easily.

1. Prerequisites

Before you begin, make sure you have the following:

• Visual Studio or any other development environment installed and configured.
• A basic knowledge of the C# programming language.
• Aspose.PDF library for .NET installed. You can download it from Aspose official website.

2. Creating the PDF document with hidden text

To get started, use the following code to create a new PDF document containing hidden text:

string dataDir = "YOUR DOCUMENTS DIRECTORY";
// Create a document
Aspose.Pdf.Document doc = new Aspose.Pdf.Document();
Page page = doc.Pages.Add();
TextFragment frag1 = new TextFragment("This is common text.");
TextFragment frag2 = new TextFragment("This is invisible text.");
// Set text property - invisible
frag2.TextState.Invisible = true;
page.Paragraphs.Add(frag1);
page.Paragraphs.Add(frag2);
doc.Save(dataDir + "39400_out.pdf");
doc.Dispose();

Be sure to provide the desired path and filename for the PDF document.

3. Search for text in the document

Next, we will search the hidden text in the PDF document. Use the following code:

doc = new Aspose.Pdf.Document(dataDir + "39400_out.pdf");
TextFragmentAbsorber absorb = new TextFragmentAbsorber();
absorb.Visit(doc.Pages[1]);
foreach(TextFragment fragment in absorber.TextFragments)
{
// Do something with the fragments
Console.WriteLine("Text '{0}' at position {1}, invisibility: {2} ",
fragment.Text, fragment.Position.ToString(), fragment.TextState.Invisible);
}
doc.Dispose();

This will search the hidden text in the second page of the PDF document and display the relevant information.

Sample source code for Add And Search Hidden Text using Aspose.PDF for .NET

// The path to the documents directory.
string dataDir = "YOUR DOCUMENT DIRECTORY";
//Create document with hidden text
Aspose.Pdf.Document doc = new Aspose.Pdf.Document();
Page page = doc.Pages.Add();
TextFragment frag1 = new TextFragment("This is common text.");
TextFragment frag2 = new TextFragment("This is invisible text.");
//Set text property - invisible
frag2.TextState.Invisible = true;
page.Paragraphs.Add(frag1);
page.Paragraphs.Add(frag2);
doc.Save(dataDir + "39400_out.pdf");
doc.Dispose();
//Search text in the document
doc = new Aspose.Pdf.Document(dataDir + "39400_out.pdf");
TextFragmentAbsorber absorber = new TextFragmentAbsorber();
absorber.Visit(doc.Pages[1]);
foreach (TextFragment fragment in absorber.TextFragments)
{
	//Do something with fragments
	Console.WriteLine("Text '{0}' on pos {1} invisibility: {2} ",
	fragment.Text, fragment.Position.ToString(), fragment.TextState.Invisible);
}
doc.Dispose();

Conclusion

Congratulation ! You have successfully added and found hidden text in a PDF document using Aspose.PDF for .NET. You can now apply this method to your own projects to manipulate and search hidden text in PDF files.

FAQ’s

Q: What is Aspose.PDF for .NET?

A: Aspose.PDF for .NET is a robust library that empowers developers to create, manipulate, and transform PDF documents within .NET applications.

Q: Can hidden text be used for watermarking purposes?

A: Absolutely! Hidden text can serve as an effective means of watermarking PDF documents, adding an extra layer of security.

Q: Is it possible to reveal hidden text in a PDF document?

A: Yes, the process of searching and revealing hidden text within a PDF document can be achieved using the techniques outlined in this tutorial.

Q: What other functionalities does Aspose.PDF for .NET offer?

A: Beyond hidden text manipulation, Aspose.PDF for .NET provides a wide array of features, including PDF generation, conversion, encryption, and more.