Hi Jackie,
I`m a veteran as far as Achilles trouble goes - had surgery on both of mine after rupturing them years ago, but pre-RA, so not related. However, one of the meds - sorry, I can`t remember which one - can affect your Achilles apparently, strange though it sounds, as I remember asking my rheumy about it, not wanting any more trouble with mine. You might like to look at your drug leaflets.
In the short term. if your Achilles is painful and feels tight, it will help if you can raise your heel - even something as simple as some felt or foam or thick card underneath your heel. Gentle stretching can help too - stand a little way away from the wall, place both palms flat against it at shoulder height, keep both feet firmly on the ground then lean your knees forward. I have to do this every day of life as my tendons are shortened after being repaired.
Physio might help, and also the orthotist.
Kathleen x