How to Replace Text in a PDF Using C#

How Do I Replace Text in a PDF?

The 'replace text' action can be applied to any PdfDocument object, whether newly rendered or imported. Use the ReplaceTextOnAllPages method by providing both the old and new text for replacement. If the method cannot locate the specified old text, it raises an exception with the message 'Error while replacing text: failed to find text '.NET6'.'

In the code example below, we demonstrate how to replace text on a newly rendered PDF document containing the text '.NET6'. This functionality is particularly useful when working with HTML to PDF conversion or when you need to edit existing PDFs.

:path=/static-assets/pdf/content-code-examples/how-to/find-replace-text-all-page.cs

using IronPdf;

ChromePdfRenderer renderer = new ChromePdfRenderer();

PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>.NET6</h1>");

string oldText = ".NET6";
string newText = ".NET7";

// Replace text on all pages
pdf.ReplaceTextOnAllPages(oldText, newText);

pdf.SaveAs("replaceText.pdf");

How Do I Replace Text on Specified Pages?

For greater accuracy in replacing text within a document, IronPDF offers options to replace text on a single page or multiple pages. Use the ReplaceTextOnPage method to replace text on a specific page and the ReplaceTextOnPages method to replace text on multiple specified pages. This granular control is particularly useful when working with complex PDF forms or documents with varying content across pages.

:path=/static-assets/pdf/content-code-examples/how-to/find-replace-text-on-single-page.cs

using IronPdf;

ChromePdfRenderer renderer = new ChromePdfRenderer();

PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>.NET6</h1>");

string oldText = ".NET6";
string newText = ".NET7";

// Replace text on page 1
pdf.ReplaceTextOnPage(0, oldText, newText);

pdf.SaveAs("replaceTextOnSinglePage.pdf");

:path=/static-assets/pdf/content-code-examples/how-to/find-replace-text-on-multiple-pages.cs

using IronPdf;

string html = @"<p> .NET6 </p>
<p> This is 1st Page </p>
<div style = 'page-break-after: always;'></div>
<p> This is 2nd Page</p>
<div style = 'page-break-after: always;'></div>
<p> .NET6 </p>
<p> This is 3rd Page</p>";

ChromePdfRenderer renderer = new ChromePdfRenderer();

PdfDocument pdf = renderer.RenderHtmlAsPdf(html);

string oldText = ".NET6";
string newText = ".NET7";

int[] pages = { 0, 2 };

// Replace text on page 1 & 3
pdf.ReplaceTextOnPages(pages, oldText, newText);

pdf.SaveAs("replaceTextOnMultiplePages.pdf");

How Can I Use a Custom Font When Replacing Text?

The ReplaceTextOnPage method also allows you to use a custom font and size. First, add the font to the PDF, then pass the font name as a parameter to the method. In the following example, I use the Pixelify Sans Font. Custom font implementation is particularly important when maintaining brand consistency or when working with international languages and UTF-8 support.

What Steps Are Required for Custom Font Implementation?

:path=/static-assets/pdf/content-code-examples/how-to/find-replace-text-custom-font.cs

using IronPdf;
using System.IO;

ChromePdfRenderer renderer = new ChromePdfRenderer();
PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Use custom font .NET6</h1>");

string oldText = ".NET6";
string newText = ".NET7";

// Add custom font
byte[] fontByte = File.ReadAllBytes(@".\PixelifySans-VariableFont_wght.ttf");
var pdfFont = pdf.Fonts.Add(fontByte);

// Use custom font
pdf.ReplaceTextOnPage(0, oldText, newText, pdfFont, 24);

pdf.SaveAs("replaceCustomText.pdf");

$vbLabelText   $csharpLabel

Advanced Text Replacement Scenarios

Beyond basic text replacement, IronPDF offers powerful capabilities for complex scenarios. When working with templates or dynamic documents, combine text replacement with other features like stamping text and images or adding digital signatures. For applications requiring batch processing, implement text replacement alongside async and multithreading capabilities to optimize performance when processing multiple PDFs simultaneously. This is particularly useful in enterprise environments where document throughput is critical. When replacing sensitive information, explore IronPDF’s redaction features for permanent removal of confidential data, ensuring compliance with data protection regulations.