No offense bro, i'm definitely not 'for' android replacing a desktop OS, but yes, it can do all those things and more. The latest versions of android on most premium smartphones come with an office clone that reads and writes various office file formats. There are bazillions of apps out there for reading and writing PDF files, etc. In addition, as far as printers...remember. Android is Linux. Printer vendors for the most part keep their printers Linux compatible. I can even write Ruby/Ruby on Rails code if i choose to do so on an android based device.
No, the real issue with Android? It's designed for a touch based device. Production level PCs are currently mouse and keyboard based devices. It will be very hard for any company to change that. Instead, if an OS vendor wants to succeed, they need to cater to that market.
Oh and to anyone claiming that microsoft is catering to that market, they aren't, and they've admitted as such, and are working to remedy that in the next major Windows release, due out in 2015.
Oh I dare say it's far worse then that. Google might go so far as to grab images only when you open emails, but this opens up the possibility of using google to DoS a target. Think: Now merely sending an email out to millions will have google request those images millions of times, potentially drowning the unsuspecting site with requests.