As the heading suggests, I'm wondering whether the abbreviation "PM" can be used for "pro memoria". I've looked it up in a number of dictionaries, but none of them list 'pro memoria' as a possible meaning of "PM".
3 Answers
It is listed at Abbreviations.com along with 212 other meanings, including Private Message, Prime Minister, Project Manager and many more of varying usefulness. (The abbreviation of Post Meridian is usually written in lower-case letters.)
The Guardian Style Guide says,
If an abbreviation or acronym is to be used more than once in a piece, put it in brackets at first mention.
So perhaps you should write "Pro Memoria (PM)" on its first appearance.
PM isn't included in this list of Latin abbreviations:
https://en.wikipedia.org/wiki/List_of_Latin_abbreviations
However, p.m. does appear in these examples:
https://www.linguee.com/german-english/translation/pro+memoria.html
https://support.getrodeo.io/en/articles/4824955-how-do-you-use-a-pro-memoria-pm-item-on-a-estimate
https://www.wordsense.eu/p._m./
Some of the Linguee sentences first introduce it with an explanation, which makes sense to do.
the proposal specifies p.m. (pro memoria).
I found the acronym in ReversoContext; one of the usage examples provided is the following: "A token entry (p.m.) is proposed for commitment and payment appropriations as well as revenue at this time.". PM means pro memoria according to the site abbreviation.com.