QUESTION: What is a linearized PDF file?

ANSWER: A linearized PDF file is a PDF file that is structured in a way that allows the first page of the PDF file to be displayed in a user's Web browser before the entire file is downloaded from the Web server. If you're developing a Web-based system that creates large PDF files for delivery to Web browsers over the Internet, you should try to make sure that your system can generate linearized PDF files. Your users might become frustrated and impatient if your system creates large PDF files that are not linearized, because it could take a long time for a user's Web browser to display a large PDF file that is not linearized.

When you're working with software that creates PDF files, the term "optimize for fast Web viewing" is often used to refer to linearization.

In this context, when we talk about "large" PDF files, we're referring to PDF files that have lots of text and graphics and contain more than a few pages. If your PDF files will be small and relatively simple, you probably don't need to worry about linearization.