I prefer PNGs to almost any other format in my documents, since they seem to be almost lossless and also dont bloat the size. Such a great work must surely be a product of a brilliant Mind. RIP Glenn Randers-Pehrson.
There are, but those are not the ones one thinks of by default when talking about PNG. If they do, they should clearly tell you they are doing something nonstandard.
The should be just plain (completely) lossless unless your image encoder is doing something evil behind your back.