For the Apple II family
The Super Serial Card II, 820-0046-(x), or 670-0020-(x) provides a two-way serial interface to a wide variety of devices, including printers, terminals, plotters, and other computers. This 129 page manual (plus Reference Card), Apple II Super Serial Card Installation and Operating Manual, Apple 030-0270-A, A2L0044 is from 1981.
Covered is extensive information about installation, printer mode, communications mode, firmware, peeks, pokes and much more...
All manuals in stock have been read and range from Very Good to Acceptable (has been wet, but perfectly readable).