I’m afraid I don’t have a solution for you but a simple pdf does not really enable any DRM or other control of access to the content. You can set it to require a password to open the file but this can be easily overcome and is more of a nuisance than anything else! Adobe does offer a product that does proper DRM but it’s expensive. You might find a program called Calibre useful - I think it will convert PDF to your choice of e-reader format (epub seems to be the most popular) and it might do some form of DRM.
i don’t know much about hosting either I’m afraid but maybe selling through Amazon would include other useful facilities as well as storing the file.
Just thinking on the DRM thing again, if it’s a book that is not likely to attract pirates it might be more trouble than it’s worth to protect it. I publish a small magazine and we take rudimentary measures to limit access to those who have subscribed - I have tried to get at it using freely available tools and workarounds and been successful but I’m not aware of any cases of it circulating in the wild as it were. Hope some of that is helpful 🙂.