When generating quote the expected dateformat is 10 OCT 2020,
How it possible to print 10 OCT 2020, date format on quote pdf
The create PDF of Quote is generated based on the fields in the object and so this change must be made at field level. And it looks like it is not possible to change the date format to DD/MMM(with letters)/YYYY at field level from out of the box functionalities. There is a salesforce Idea for the same.
However, you can try the workaround as below:
TEXT(DAY( expirationDateFormula)) & CASE( MONTH( expirationDateFormula) , 1, "-Jan-", 2,"-Feb-", 3, "-Mar-", 4,"-Apr-", 5,"-May-", 6,"-Jun-", 7,"-Jul-", 8,"-Aug-", 9,"-Sep-", 10,"-Oct-", 11,"-Nov-", 12,"-Dec-", "invalid") & TEXT( YEAR( expirationDateFormula) )
You can replace expirationDateFormula with the field you want this formula to work on.
You would now have 2 fields, one with the date as per salesforce standards (with digits for the month), and one with your preferred format (with letters for the month).
Now add this field to Quote Templates . The "create PDF" would show it in the desired format. I have tried it in my org as below