I've been playing OS update vs file transfer capability games with my Nexus 7 2013. Apparently, my Android device bumped up to the Marshmallow OS without my knowledge while I was trying to figure out why Lollipop lost the ability to transfer files to my PC over the USB cord. After giving my head a trim via hair-pulling (both of them), I found a nugget of knowledge that works on late Kit-Kat on up.

Step one - you need a USB OTG (On The Go) charge/data cable compatible with your device. I had one that was in the box, but I wore that out pretty quick. Given I use my Android device as an extended dashboard, I wanted a cable that tucked nicely out of the way - so I bought this [ ] and it works.

1. Android Settings, go to the bottom of the list - "About Tablet"
2. Tap About Tablet 7 times - you will then have the ability to activate "Developer Options". Some powerful (and crippling) stuff resides in there, so you really don't want to run amok.
3. Activate USB Debugging.

I rebooted my Android device to get everything fully activated, then I plugged into the PC with my fancy-schmancy OTG cable. Nothing happens on the tablet except a small icon appears on the drop-down menu (upper-left corner). I swipe the menu down and change the USB mode from Charge to File Transfer. The PC then shows the files in the Android device. This has worked on Windows 7, 8, and 10.

That was the technical way, but emailing the files or sending them up to your cloud storage is less-involved and built into the system - if you have a file explorer app. I haven't tried attaching files from an email app - and that may be the most painless method.