What is PDF Linearization (Fast Web View)?
TL;DR: Linearization is a PDF optimization technique that reorganizes the file structure so the first page can be displayed immediately while the rest of the document continues downloading. This is critical for large PDFs viewed in web browsers.
A linearized PDF rearranges its internal objects so page 1 data appears first in the file. Without linearization, a browser might need to download the entire 50MB file before showing anything. Linearized PDFs provide a "fast web view" experience.