Well, that ppl can't see the changes immediately is a problem we have to tolerate for now. I could place a list on the right-hand side which shows who has submitted which changes. That feedback could be helpful, but the base version of the document would still be unchanged. The PDF won't see those changes anyway, until I update it. The thing is, if I let anybody edit and save the text it could create conflicts or even attract vandalism. And creating a login system with rights management is far too complicated and time-consuming.
PatchPad is something I just wrote in a couple of days. It may be simple but it does its job very well, and it certainly is much better than reading forum posts where users have to explain to me where to make corrections.
You're right, two users could make the same correction to the same line, and they may be in conflict. But since I review the changes I will choose to apply the ones that make sense. Not a huge issue I think.
Regarding SVN: I already use a "repository system" called Git at:
http://github.com/alsanaaziz/salam (The files are fetched from there and cached by PatchPad.)
Now the problem is, a lot of ppl don't know what these systems are (let alone know how to use them). That's why I created PatchPad, so that
anybody can submit patches to me. The great thing about PatchPad is, that you can choose to edit ANY document in my repository (URL: pad.php?doc=...).