Is it proper to use the abbreviation pc instead of cc? I have always used the abbreviation cc as a courtesy copy, however, I am told to use pc for photo copy at work. I have never seen this abbreviation used before outside of this office.
I've not come across pc before, but of course, within a company, whatever policy is set by the bosses, is correct.
Courtesy Copy is a new "made-up" word. The first "c" has always stood for carbon. We have not made carpons for years. The letter "p" stands for photo and this term has been around for about 30 years.
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I've never seen "p" either. Can I ask where you've seen that?

These days, they're not really photocopies either - you just print multiple copies of the original letter.

But as Nona says, it's whatever the convention is in your company.
We use PC in our company and I always thought it meant Paper Copy. I just put the names of the people in that spot who will be receiving hard copies of the document.