No, I didn't pinch a regular pad in the chuck.
You can buy them at hardware stores; mandrels and round pads that screw into the mandrels. I forget what I bought last; it's been awhile and I still have some left.

I don't use a really high DPI setting. Try lowering it, if you can. 300 DPI should be sufficient.

As far as the trace edges being ragged; it could have been a number of reasons. Maybe your iron isn't really flat on the bottom. Try keeping the iron in one place for 20 seconds, and then moving it to another place for another 20 seconds. You may need to use more padding under your board. Maybe the surface your board is on isn't particularly flat.

Too much pressure wouldn't cause the edges to be ragged.

 

As far as the trace edges being ragged; it could have been a number of reasons. Maybe your iron isn't really flat on the bottom. Try keeping the iron in one place for 20 seconds, and then moving it to another place for another 20 seconds. You may need to use more padding under your board. Maybe the surface your board is on isn't particularly flat.

Too much pressure wouldn't cause the edges to be ragged.

Yeah I think too much pressure. The first time I did not press hard enough.

There are only a few small spots where it happened. Otherwise they look pretty clean.

Broke my first bit. Note to self: Remember to extract the bit all the way out of the board before moving it. And don't do fine work like that when you are tired!