How to Programmatically Find & Replace Text in PDFs

Summary: If you’ve ever had to update a specific term across even a handful of PDF documents, you know how cumbersome it can be. Programmatic Text Editing is a powerful tool that brings intelligent, layout-aware find-and-replace to PDFs. It handles scaling, security, and complex reflow for you. This blog explores programmatically finding and replacing text using Apryse Server SDK and the PDF Editing add-on. It also covers use cases, how to get started, and some commonly asked questions.

PDF is the standard for professional, non-negotiable documentation. The problem is that it’s a headache when you need to change things in multiple spots in a document or across multiple documents.

If you’ve tried to automate this task, you’ve probably run into problems. For example, you get the old vendor name replaced with the new one, but the paragraph is now split up, the text runs into the margin, or the whole layout just looks out of place. This is because most tools treat the PDF like plain text, ignoring the crucial details of layout, fonts, and spacing.

Manual editing can’t be done at scale as it’s slow, boring, and guaranteed to introduce human error, and desktop editors can’t process thousands of files without crashing your machine. This is where Programmatic Text Editing comes to the rescue.

In this blog, we’ll explore this feature available with the Apryse Server SDK and PDF Editing add-on. I’ll be using C# for this example, but the code is available in other languages like C++, Java, and more.

Think of it as find-and-replace, but with the added benefit of handling document layout. This capability is built into our core PDF engine, meaning it operates at the object level of the document, not just on the visible text layer.

Key Capabilities

When you replace a string, the system doesn’t swap the new text for the old in the same spot, hoping it fits. It dynamically recalculates the page structure to absorb the change through layout-aware reflow.

This process ensures that your updated document looks exactly as if the change was made during the original design phase.

Let’s look at some examples of where programmatic find and replace can be used.

Enterprise Legal: A company name or regulatory clause changes, requiring updates across thousands of archived documents.

Write one script to find the old text and replace it with the new one, ensuring every single document maintains its formatting and signature block integrity.

Government/Compliance: New legislation requires a specific disclosure wording to be updated across hundreds of public forms and notices.

Automate the update across the entire document library in a secure, audited server environment, ensuring compliance and consistency.

Publishing/Education: A major rebrand means updating logos, brand names, and contact information across a massive library of handbooks, brochures, and course materials.

Process the entire brand rollout using a script, trusting the reflow engine to handle the visual changes without requiring designers to manually check every page.

First, you’ll need to download and set up the Apryse Server SDK.

Note: You will also need the PDF Editing add-on to use this feature.

Next, we’ll look at the code that’s needed to find and replace a word in a PDF document. In the following sample code, I chose to use C#, but the code is also available in other languages like C++, Java, and more.

Note: This code sample is just the code that performs the process. See our sample page for the full code.

And there you have it. It’s really that simple with just a few lines of code to specify the find and replace options.

In this case, we’ve told the code to search for whole words that are an exact match of the word “the” including case and replace it with the phrase “THE INCREDIBLE”. We also set some options for the replacement, such as the reflow type and alignment.

How is this different from a basic text search-and-replace function?

A basic function just swaps characters, often running into issues with the visual structure. Being layout-aware, programmatic find and replace dynamically reflows the surrounding text by moving it up or down to keep the paragraph structure intact.

Is this secure enough for highly regulated documents like those under HIPAA?

Yes. The power of a server-side SDK is that the processing happens entirely within your security perimeter. The documents never need to be uploaded to an external vendor’s cloud service.

Does the reflow engine handle non-standard fonts or complex layouts?

Because it’s built on our native PDF editing engine, it respects the original document’s object model, including embedded fonts, spacing, and structural elements. The edits are handled as if they were part of the initial document creation, leading to high fidelity even on complex designs.

Can I use regular expressions for my search patterns?

Yes. The programmatic nature means you can leverage powerful search capabilities, including regular expressions, to define complex and flexible find-and-replace rules.

Developers know that their time is too valuable to spend piecing together unreliable text replacement scripts or relying on desktop tools. Programmatic Text Editing, available through the Apryse Server SDK and PDF Editing add-on, is an essential tool for anyone managing critical, high-volume PDF workflows and provides the security, scalability, and layout fidelity you need.

Check out the text editing documentation to get started or start a free trial.

Contact our sales team for any questions or jump on Discord for support and discussions.