At the most basic/cheap level you could use drop box and crash plan which was where I was going before you mentioned the B word. PDF's and mac's to me usually means graphics/artwork so how big are those PDF's going to be and is it realistic to download them on mobile?
Dropbox keeps a local copy on each mac it's installed on and allows you convenient access via mobile devices via an app for the main platforms. Would I trust it with sensitive/business data? Probably not, but I know others do. Crash Plan will backup each mac to the other, this obviously depends on space available, a NAS or external drive is an option as is another computer off site, it also offers paid cloud backup options. While this sort of set-up is probably fine for home user now you've mentioned business use i'd be a little more reserved. Dropbox could be replaced with your own in house NAS or server with a VPN back to the office assuming the mobile devices support a decent VPN client. A lot of current gen NAS'/distro's have Time Machine support baked in so this would also take care of the mac backup situation. Synology have a support life cycle based on 3 years for major DSM support which personally I don't get on with but it is an off the shelf solution where you just add drives. The other option is a basic server set-up, something like a Gne8 Microserver is cheap, add RAM and 2-3 drives and whatever NAS distro you prefer, xpenology or Un-Raid etc. are popular. You could also run the VPN from one of the mac's and connect the mobile devices back through that for little/no cost.