TLDR: run this script to get S300, S1100, S1300, or S1300i models working in Linux: script
All four of these scanners require firmware to be loaded onto them from the computer. You can find these firmware files around the internet, but I've uploaded them here as well:
You must copy the firmware you downloaded into a location where SANE (the scanner daemon) can find them. For most cases you just need to move those files into /usr/share/sane/epjitsu/.
You then need to tell SANE where it can find the firmware files. To do that you should edit /etc/sane.d/epjitsu.conf and add the following for your scanner (if it's not there already)
# Fujitsu S300
firmware /usr/share/sane/epjitsu/300_0C00.nal
usb 0x04c5 0x1156
# Fujitsu S1100
firmware /usr/share/sane/epjitsu/1100_0B00.nal
usb 0x04c5 0x1200
# Fujitsu S1300
firmware /usr/share/sane/epjitsu/1300_0C26.nal
usb 0x04c5 0x11ed
# Fujitsu S1300i
firmware /usr/share/sane/epjitsu/1300i_0D12.nal
usb 0x04c5 0x128d
Now you should just need to logout, and log back in for the drivers to load up correctly. You can try running scanimage -L to see if your scanner shows up.
On openSUSE it seems that you also need to the YaST Scanner tool in order to get everything setup correctly. It will likely tell you that you need to download firmware, but if you did the previous steps you should be able to just press OK, and your scanner should show up.
I'd recommend simple-scan if you just want somethings to quickly scan documents, but gscan2pdf is the only program I've found that can do duplex scanning.