Gerber files, i.e. technical drawings of printed circuit boards (PCB) can be typically saved to other gerber formats, as well as exported as images or PDF documents for publishing / sharing purposes. Such gerber to pdf conversion can be typically performed with a dedicated export function in a program that works with your particular gerber file. Just keep in mind that the resulting image will be just that - a picture, and you won't be able to work with it in gerber software, but a graphics editor.
Open GERBER file Open PDF fileA CAD and Gerber conversion software
A gerber converter