I just recently updated to Reader X (on an XP machine) and notice that you can no longer spool more than 999 copies to print at a time. The old version also had only a 3-digit field, but you could type in 999 and arrow up to spool over a thousand at a time. Now with Reader X, it won't go over 999 no matter what you do. For my work I usually have to print tens of thousands of copies at a time, and having to do it in increments of 999 is really slowing me down. Is there a way to do this that I'm not aware of?
It seems the maximum number of copies possible in Reader X is indeed 999. You can request Adobe to change that.
A temporary workaround could be to print using a script and a loop, but that might over-flow the printer since it will not be 1 command to print 1000 times, but 1000 commands to print 1 time, for example.
A work around I use is to "print" a number of copies to a new PDF file... say 500... then use that mutiple copy version to print to the printer. So to do 10,000 copies, print 500 to the file, then take file and print 20 copies. Not a perfect solution but saves time over doing the print 10 (or more) times.