In Adobe Acrobat and Adobe Reader, the best way to see if a PDF is Linearized is to look at the Document properties. If the file is a linearized PDF, the item Fast Web View will display Yes.

How do I know the extension of a PDF?

If you're using Adobe Acrobat to read PDF files, choose File > Properties and click on the Description tab to view the format of the document. You can see the format of the page under Page Size.

Is PDF linearized?

A linearized PDF file is a special format of a PDF file that makes viewing faster over the Internet. Linearized PDF files contains information that allow a byte-streaming server to download the PDF file one page at a time.