Flatten or rasterize a PDF to make it read-only?

Kostas, Developer

Sometimes, when working with a PDF document, you might wonder how to restrict the file from editing. You may want to make it read-only for various reasons, such as when a PDF document contains a fillable form, and you want to ensure that no one modifies it after filling it. Flattening a PDF can be a great way to protect the content from easy editing or manipulation. Once flattened, extracting and modifying the original text or vector elements becomes more challenging. ConvertAPI provides two ways to achieve this, and we will discuss both converters in this article.

● Flatten PDF API retains vectorial graphics

Flatten PDF API converts a PDF file with multiple layers, annotations, or transparency into a single, flat layer. This means that all the elements in the document become part of a single image, and the document loses its layered structure. Flattening helps ensure the document looks the same across different viewing environments or software applications. Flattened PDF will retain its vectorial properties and can be upscaled without losing quality. All it takes to flatten a PDF is a single HTTP request:

curl -F "File=@/path/to/my_file.pdf" -F "StoreFile=true" https://v2.convertapi.com/convert/pdf/to/flatten?Secret=your-api-secret

When flattening a PDF, you can also flatten the text so it cannot be selected or copied. It will redraw the text into lines and shapes to prevent it from being extracted or modified. This technique is useful in situations where you want to make the PDF read-only. However, it has drawbacks; for example, it may increase the file size.

● Rasterize PDF API improves rendering and compatibility

Rasterize PDF API endpoint converts the vector-based content of a PDF file into a raster PDF. You can think of that as converting the PDF to bitmap or raster image format, such as JPEG, PNG, or TIFF, and then creating a PDF from these images. It will be a single-layer, image-like document with no editable controls or selectable text. To rasterize a PDF, all you need to do is make an HTTP POST request to our Rasterize PDF API endpoint:

curl -F "File=@/path/to/my_file.pdf" -F "StoreFile=true" https://v2.convertapi.com/convert/pdf/to/rasterize?Secret=your-api-secret

Converting a PDF to a raster format can ensure better compatibility and print quality, especially when dealing with complex vector graphics. Rasterizing a PDF can also reduce its file size. It's important to note that while rasterizing has advantages in specific situations, it also has drawbacks, such as loss of scalability and resolution.


When it comes to flattening a PDF, it's important to consider your specific requirements and document workflow. For instance, if you need to preserve vector-based content and scalability, Rasterize PDF API may not be the best approach. Similarly, using the Flatten PDF API to flatten the PDF can result in a larger file size and loss of the ability to interact with individual elements.

It's worth noting that although flattening or rasterizing the PDF can make it more difficult to extract content, it's still possible to recover text using OCR and other software. Therefore, you should carefully evaluate your needs and choose the most appropriate method of PDF flattening for your particular situation.