I had the same problem in the last few weeks of my pregnancy and as soon as I noticed the pitting I rung my midwife in a panic as I had heard that its a sign of pre-eclampsia but as long as your blood pressure is normal then your fine. Mention it to your doctor/midwife when you see them next. Just a word of warning - the swelling probably wont get any better till after you give birth! (it certainly didn't for me anyway) but try convincing someone to give you a foot massage, it feels heaps better (well for a couple hours anyway) other than that just try to keep off your feet as much as possiable - its a handy excuse for crashing out on the couch with a book!!!
Good luck!!!