Mostly a post to help my future self and others trying setup a ScanSnap S300 in Ubuntu
Things should mostly be setup by default, but there is one tricky bit. You need a file from the windows drivers. I had an old hard drive w/ my previous install to copy from. You might need to set it up in a virtual machine or another windows machine to get the file.
Make a directory for the file at /usr/share/sane/epjitsu/
Copy from C:\Windows\SSDriver\S300\300_0c00.nal to /usr/share/sane/epjitsu
chmod 755 /usr/share/sane/epjitsu/300_0c00.nal
Make sure you scanner is found using
If it is you can do scanimage -L or sudo scanimage -L to see if things are working.