Re: PA28-161 POH Revision
When I ordered the revisions for our aircraft from the UK dealer I was told it was £5 for each copy and I had to give them the aircraft s/n so you can't just photocopy the revision for each aircraft. Then subsequently I was told that they could send me a copy and didn't need a serial number (that was when I found all the PA28-161 POHs were affected - we have two types on our fleet, different MAUW)). At the moment I'm watiting to see what arrives then I can work out if I have to order more copies.
Some manufacturer websites are excellent like the Lycoming one with most of the Service Letters, Bulletins etc available on line plus a load of other handy hints. Piper just want to sell you a new airplane and after that, tough!