And then...it didn't - for no apparent reason - I think ??
Before making this post I searched here in hopes of any simplified guide as well as generally and visited this as well:
https://wiki.ubuntu.com/DebuggingPrintingProblems
The main problem for me was when trying to print in any form from a web page, like the receipt I needed a paper copy of yesterday - but all I got was the dialogue box saying 'an error occurred while printing'.
I had to go & pick up that order - minus any receipt - so I left it that way.
Came back to it today & got the same error message, so I looked through http://127.0.0.1:631/admin/ - the logs there, but the volume of info is way beyond my knowledge level.
All had been fine with both PDF 'printing' & my Brother HL-5050 on USB for a very long time, and then making PDFs gave that error, and after a while it was all I got, even when trying to request a print preview...but just now I went further & tried printing from Nomacs - which worked for both, then from Leafpad - which also worked - and finally back to that receipt in the browser & that worked both ways as well.
I hope this never becomes a problem again - but if/when it may - is there any really clear & maybe simplified guide that goes sort of step by step to help in tracking down & recovering from a vague printing error like what I got ??
Thanks for any guidance in this matter.