Two years ago I tried a few options (probably because I stumbled over some very badly formatted programs, usually I don't encounter anything remotely as bad). I tried Piew, Notepad++ with 3GP plugin and Progress Developer Studio.
In my experience PDS was best, then 3GP and then Piew (closest to our coding conventions), but none was actually very good, they would all make correctly formatted code worse. I would only use these on code where the formatting is hopeless anyway as a first step. They might have gotten better in the meantime, though.
The developer of Piew is quite approachable, I reached out to him about some bugs and he fixed them.
As a starting point for a program that is in a horrendous state, the indentation correction in PDSOE isn't actually that bad. Ok, so it probably doesn't match your coding practises, but it's a starting point to make sense of the blocks. Which is what I often find the hardest part. Then you need to use some brain-power to make it all right again.
Here is the famous beauty.p program written in Progress Version 6 by Warren Bare while at Progress. It reformats Progress source code in "standard" form. There is also an updated copy, beauty8.p, for Progress V8 and above that was written by Matthew Brooks.
it has some small improvements on the top. Also there are some manual beautifiers based on user selection: ALIGN DEFINE VARIABLE and ALIGN ASSIGN functionality - can reformat definition, assign sections to the same "columns". On not complex sources works very well.