The nimbus did not have an inbuilt Parallel port.
To gain one required the use of either a Piconet box, or this add-on card.

It also provided a BBC compatible user port.

Specification:
26-way BBC-compatible parallel prnter port
20-way BBC User Port
+5v DC Supply 1.70A
+12v DC Supply 0.65A

Pin Number	Signal	Purpose
1	CA2	Strobe
3	PA0	Data Bit 0
5	PA1	Data Bit 1
7	PA2	Data Bit 2
9	PA3	Data Bit 3
11	PA4	Data Bit 4
13	PA5	Data Bit 5
15	PA6	Data Bit 6
17	PA7	Data Bit 7
19	CA1	Acknowledge
Even except 26		Signal Ground

An article from 'Electronics Education' in Spring 1990 gives some further details: