Is it wrong to use the occasional office stationary for personal use? 

It is normally allowed for employees to use ‘a little’ stationary for personal use. This extent, which varies according to one’s situation, is permitted to use. More than this would be disliked or, if excessive, unlawful (haram).

The criterion is:

a) what is accepted behavior in our office?

b) if my manager saw me, would they mind or not?

This is based on the fiqh principle: “That which is customarily permitted is legally permitted.” [Ibn Nujaym, al-Ashbah wa’l Nadha’ir, 1.307; Majalla (item 43)]

And Allah alone gives success.

Wassalam,
Faraz Rabbani