This is due to the disconnect in web vs print disciplines. They have a print oriented designer do the menu, and use PDF for print and for web. But invariably on

This is due to the disconnect in web vs print disciplines. They have a print oriented designer do the menu, and use PDF for print and for web. But invariably on a mobile device it downloads a persistent PDF file, and has a net negative experience as a media type, size is always more bloated than HTML/CSS equivalent not least of which is due to the embedding of fonts in the PDF and superfluous print quality resolution images. The restaurant industry is poorly served by having these disciplines separated. It's been possible to do high quality printed output with HTML/CSS for a decade if you have a web designer familiar with it, but sadly too many aren't and so the restaurant has the menu done by a traditional print designer.