We do not have any printer specific examples or reference designs. The best place to start is with the EZ-811HS development kit for the SL811HS. This kit comes with sample firmware that provides all of the fundamental routines to enumerate and communicate on a low level with most USB devices (can do control, interrupt, and bulk transfers). You can take these fundamental routines and build upon them to create a "printer driver". The ability to do bulk transfers is already in place. All of the files including sample code and documentation for this kit are available from our website. From the home page if you select products->Embedded Hosts->SL811HS->EZ-811HS.
Alternatively, if you are running an RTOS that already contains printer class drivers, you may simply be able to add one of our Host Controller Drivers (HCD). We have HCDs available for WinCE, Linux, and VxWorks. An RTOS with printer drivers, our HCD, and our SL811HS hardware together would create a complete USB solution.