OK,
funny as hell,
I tried to resize from A4 to A5 again on other computer,
this time works without error message.

Now my only problem is,
the document became 11000 pages from 5000 pages, which is ok,
some lines automatically broke into next line after reached the slide,
but some doesn't, don't know why.

So,
how do I tell MS word to break all these out-page lines into next line?