How to Convert JPEG to PDF in C#

Introduced in 1992, JPEG has been the most widely used image compression standard in the world, and the most widely used digital image format. It’s estimated that as of 2015, several billion JPEG images are produced every day. We love JPEGs for their compatibility, but they have a major organizational flaw in that they are loose files. When you have twenty images for a project, sending them as separate files is a nightmare for the recipient and a branding risk for you.

JPEGs don't support layers of metadata, bookmarks, or security permissions in the way a document does because they are just a grid of pixels. When you need to ensure that an image is viewed at a specific scale or protected from unauthorized editing, a raw image file falls short.

Converting a JPEG to a PDF wraps that pixel data in a professional container. It transforms a loose image into a formal document that looks identical on a phone, a tablet, or a high-end workstation. You can work with images at a low level like producing a black & white PDF file for a better-quality file for OCR text data extraction, or with higher level methods such as the one we’ll explore here.

In this blog, we’ll look at the why and the how-to for converting JPEG to PDF using the Apryse Server SDK, and cover some common questions.

There are several reasons why your creative team would prefer PDF for the final hand-off:

Document Integrity: A PDF preserves the aspect ratio and resolution of your JPEG, ensuring it isn't accidentally stretched or compressed by a preview tool.

Security: Unlike a JPEG, a PDF can be password-protected or restricted so that people can view the work but not print or copy it.

Multi-Asset Packaging: You can combine dozens of JPEGs into a single, paginated PDF.

Searchability: While the image itself is pixels, you can overlay invisible text (for OCR purposes) or add comments and annotations on top of the image within the PDF.

First, we’ll need to get started with the Apryse Server SDK. Follow these steps to download and install the SDK and then get a trial license key if you don’t already have one.

After that’s done, you’re ready to move on to the next section for the code to convert your JPEGs to PDFs.

We’ll use the pdftron.PDF.Convert utility class for our conversion example. It’s a high-level tool that handles the image processing for you.

In this example, we’ll use C# but note that the code is available in other languages like C++, Java, JavaScript, and more. The following code is a basic sample for handling the conversion.

For a full code sample with other document and image conversion options, see the documentation.

If you’re looking for more examples of converting JPEG to PDF using other programming languages, see these blogs:

And here’s one for converting PDF to JPEG using C# and Java.

Does converting a JPEG to PDF reduce the image quality?

No. By default, the conversion process embeds the JPEG data directly into the PDF. It essentially acts as a wrapper, so your pixels remain exactly as they were in the original file.

Can I combine five JPEGs into one PDF? 

Yes. You can loop through your files and call the conversion method for each one within the same PDFDoc object. Each image will be added as a new page. See this blog for more details.

How do I handle the file size if the JPEGs are large? 

The SDK includes an Optimizer class. After you convert the JPEG to PDF, you can run an optimization pass to downsample the images or adjust the compression to make the file more email friendly.

Do I need to know the image dimensions beforehand?

No. The Convert.ToPdf method automatically detects the dimensions of the JPEG and creates a PDF page that matches those exact proportions.

Is it possible to convert a PDF back into a JPEG? 

Yes. You can use the PDFDraw class to render any PDF page back into a raster image format like JPEG or PNG.

As you can see, converting JPEG to PDF is simple and easy with just a few lines of code.

Converting JPEG to PDF is one of the most common tasks for content teams, and it doesn't have to be complicated. By using the Convert utility in the Apryse SDK, you can build a reliable tool that handles your assets professionally without the need for additional software.

Try the Apryse Server SDK with a free trial or check out the documentation.

You can also contact our sales team for any questions.