I use UPDF since approx. 1 year. I use it every day. It allows me to open PDF files (simple but important task!).
I also use it for minor changes on already gerenated PFD. Very good for it !
The only thing that may be optimized is that this is a bit slow to open / Load document. Also, I find the software bekoming a bit too complex. Too much features added again, and again. For exemple we got a kind of AI functionnality. (I don't even know what it does, but really doesn feel the need to use AI for my PDF files..). Maybe this is the reason why the files are opening slowly ?
My advise : Keep it simple, fast and reliable. don't fall in the trap of adding 1000 functionnalities, that users actually never asked for.
Nevertheless, I would still highly recommand it as I'm a satisfied user.